I'm worried not so much about breakage/leakage as you can just take precautions with extra padding and good packaging, but more about oxidation with the bottles being shaken up during hot weather. We're hoping to be able to submit beer for a brewing competition from South to North China, where it's currently around 38 degrees.
All you can really do is ensure that your fermentation, sanitation and bottling practices are as sound as possible. You should (as you seem to) definitely expect that your beer will see the worst conditions you could think of, chiefly: heat and cold (and rapid and frequent swings between the two); and near-constant agitation.
To combat this, you'll want to do your best to exclude oxygen pickup during fermentation and (especially) packaging (as this will be the most likely source of rapidly-developing off-flavors), to cold-condition your beer (if possible) as cold as possible (to help minimize the development of haze, or worse, flakes), and to keep things as sanitary as possible (since the high temperatures will serve to exacerbate any shortcomings).
Basically: don't rack before bottling unless there's a really good reason to (and purge your vessels well with CO2 or nitrogen, if you do); cold-condition (if you can) as low as possible, to help with haze stability; bottle-condition, to help scavenge any oxygen present; fob your bottles properly (either spray a quick blast of water/sanitizer into them, or tap the bottle firmly) to ensure that you're capping on foam; and keep sanitation as tight as you possibly can.
You should probably also try to use nice bright beer, as too much yeast in the bottle will likely lead to off-flavors as it deteriorates.
Google for polystyrene wine storage. Those containers are great for shipping beer and you can get them in various sized.
When you have your container get bubble wrap and place a double layer of bubble wrap in the bottom of each pocket.
Cool your beer to close to 0C, Don't worry, it won't freeze. Just before shipping, remove the beers from the fridge and wrap with news paper and place in pocket. Fill remaining open space with news paper, close container and have it shipped.
The bubble wrap will protect against damage from someone putting the box down hard and the news paper and polystyrene will help insulate the temperature. If you are worried that the news paper will leave odors on the bottles that the judges may pick up on, wrap your bottles in plastic (Glad/Saran wrap) before wrapping in news paper.
Put a FRAGILE and THIS SIDE UP sticker on the container. :)
Give a bottle to the postman.
The most reliable way to get you beer shipped in China is as checked baggage on a plane. It will be quick, partly air conditioned and only a few people will have the opportunity to throw it on the ground. I don't think you could even get on a train with bottles, because of the restrictions on liquids.
FYI, local pro brewers and european importers only ship beer warm, because refrigerated shipping is almost nonexistent in China.