First thing first, it's officially forbidden to camp anywhere on the Great Wall. When you visit, you will see many places even having signs that specifically says no camping allowed
However, the rule is basically not enforced outside of the popular sections (as of 2019 anyway). Lots of locals and foreigners do it every year. Because the Great Wall is so long - over 13,000 miles in total - most sections are simply unpatrollable. Also, local authorities turn a blind eye to it and allow some tour operators to sell camping tours to the wall (obviously get get a cut of the profits) mostly to foreigners. That being said, you're still doing it at your own risk
I highly recommend going with one of the tour operators (I've listed some well rated ones below), for three reasons: it's very hard to find gear rental in Beijing (you most likely have to buy them), the logistics of getting to the campable sections of the wall is not easy, and operators probably have connections to provide legal cover. A two-day hike should cost $100-$300 for a large group, all included. Here's six highly rated and reputable operators you can check out:
Great Wall Hiking: Tripadvisor, website. This is the one I went with on my first camping trip. An all-local team and extremely knowledgeable about China and the Wall. You won't go wrong with these guys
But it's definitely doable on your own; I've done it twice on my own and once with a tour. If this is what you want to do, the most important thing is deciding which section of the wall you're going to camp on. There are two considerations for this decision:
Accessibility: you can find almost limitless number of spots to camp along the 13,000-mile length, but most of it are in the remote hinterlands or desert regions of China that's very difficult for even locals to access. So for most visitors, your choices are limited to the sections of the wall close to Beijing
Popularity: the popular sections of the Great Wall around Beijing are going to have more visitors and more oversight from authorities that will effectively prevent you from being able to camp. For this reason, you can eliminate Badaling, Juyongguan, Shanhaiguan, Simatai, Mutianyu, and Jinshanling
Based on my experience and research, these are the campable sections of the Great Wall that the vast majority of campers choose, ordered by popularity amongst campers:
Jiankou (箭扣): this is a very challenging section of the great wall that's mostly unrestored and with some very steep parts (like Sky Stairs). You need to get to the village of Xizhazi (西栅子村)and start hiking from there. You can go either west towards Huanghuacheng, or southeast towards Mutianyu. There are many camping spots along this stretch in any of the watchtowers. Getting to Jiankou from Beijing.
Gubeikou (古北口): considered a "wild wall", meaning completely unrestored. It's not particularly challenging of a hike, but it's very remote and you can hike for hours without seeing anyone. It's my favorite place to camp because of its isolation and ruggedness. The wall here feels like Roman ruins. You start from the town of Gubeikou (古北口镇), and then hike eastward towards Jinshanling. Camp here overnight in any of the watch towers or even on the wall itself, and then continue until you get to Jinshanling where you can get a ride back to Beijing. Getting to Gubeikou from Beijing.
Huanghuacheng (黄花城): it's actually a pretty well restored section of the Great Wall, and popular with a lot of camping tour operators so expect to find other campers here. When you go there on your own, you will arrive at Xishuiyu Scenic Area, which is where the Great Wall is submerged into a body of water called Little West Lake (Xiaoxihu). From this point, you can hike east or west. Along the way you can find an unclaimed watchtower to settle in for the night. There's also a designated camp site at Xishuiyu as well. Getting to Huanghuacheng from Beijing.
Chenjiapu (陈家堡): even though it's close to Badaling, which is packed with tourists, this section is actually extremely unknown. You'll encounter even fewer hikers and campers here than any of the ones campable sections I already mentioned (especially compared to Huanghuacheng and Jiankou). Many sections of the wall is basically a pile of stones. You should have no issue finding camping spots. To get here you need to get to the village of Chenjiapu (陈家堡村). Getting to Chenjiapu Great Wall
Longquanyu (龙泉峪): another very off-the-beaten section where you're unlikely to run into many other hikers and campers. Start from the village of Longquanyu (龙泉峪村), then hike east towards Xishuiyu. You'll see lots of spots to pitch tent either in a watchtower or on the wall. This hike is relatively flat and not that challenging. Getting to Longquanyu Great Wall
Here's a map of all the sections mentioned above. Click on the pin to see section name:
How long to camp for:
Most people camp overnight and return to Beijing the next day. Most of these sections aren't that long 7-10km, so 2 days is sufficient.
The longest I've done is 3 days 2 nights. But I've met people who spent 4 days and 3 nights. You might get bored after the second day
When to camp:
Since all camping is technically illegal and people do it anyway, there's nothing preventing anyone from camping any time of the year
Late April - mid October is the nicest time to camp in terms of weather. Outside of these months it gets really cold at night
Winter camping is doable but very challenging; only do it if you're in good physical condition and have lots of hiking experience. The steep walls, bitter cold, storm, and slippery surface, all make for quite a dangerous combination
After you've decided which section to visit, then you need to start preparing your gears and supplies
Don't bring more than the bare essentials. Depending on which section you choose, there will be many steep stretches you need to climb or descent
Gears - nothing special just your standard camping gear:
Tent: check the weather you might need waterproof tent
Sleeping bag: you'll be sleeping literally on rocks so get comfortable ones
Supplies: water, food and snacks, toilet paper, sanitary wipes, garbage bags, extra warm layers (it can get 10 degrees colder than Beijing on the Wall at night), cash (you may need help from locals finding the start of those less visited sections of the Great Wall)
It's almost impossible to rent gears in Beijing. Camping is not a popular activity in China. Instead, you need to buy your gear unless you're going with a camping tour. Decathlon is probably the most popular chain of stores to get this kind of stuff from in Beijing, it's a French company I think. Sanfo is another chain of stores you can get outdoor gears from in Beijing
In the almost unheard of event that you're caught by a security guard, know that in China everything can be solved by cash. If it's only a single guard, ¥100-¥200 will probably send him away. Just don't act entitled, be humble when you give them the cash. No one likes a brat
Clean up after yourself and don't leave anything behind, not even toilet paper