If your film is slower than ISO 800, going through CARRY-ON x-ray twice or even four times (assuming you have a connecting flight) will do it no harm. How do I know this? I flew from Washington DC to Cambodia with I forget how many rolls of film - some black-and-white, some color, some Kodak T400CN (black-and-white that you process in C-41 color chemistry), and even a few rolls of Kodak HIE 35mm infrared. On the way TO Cambodia, I flew from DC to New York, changed planes, then went from New York to Amsterdam, had a layover, then on to Singapore. Two days in Singapore, then Singapore to Cambodia (Siem Reap). Five days in Cambodia, then from Siem Reap to Phnom Penh, Phnom Penh to Singapore, half a day in Singapore, then Singapore to Amsterdam, layover in Amsterdam, Amsterdam to New York, and then New York to DC. On the way to Singapore, I had the film hand-checked at every stop (even though we never left the departure area in Amsterdam, there was still a baggage scan when re-boarding the flight). On the way to Cambodia from Singapore, the security boy couldn't grasp the idea of a hand-check for my film, so I let it go through instead of fighting with him and missing my flight. I had the same thing in Cambodia when returning to Singapore. The X-ray machines in Singapore are ultra-modern, so I wasn't too worried, but the X-ray machine in Cambodia was positively ancient. I figured if anything would dose my film to ruin, it would be the Cambodian X-ray machine, and any subsequent exposure wouldn't make a bad situation any worse so I let it go through all the remaining checkpoints without a hand inspection. So on the return, it got dosed twice in Cambodia, once in Singapore, once in Amsterdam and once in New York. Nothing got fogged or damaged, not even the HIE. Your film gets more radiation exposure while in flight at 35,000 feet than it does going through five X-ray passes.
Frankly, I would be more worried about getting film processed in China than X-ray fogging. I've had terrific experiences with getting C-41 processed locally in Bangkok, and not-so-great experiences in Buenos Aires (at a Kodak franchise lab no less). I'd do some online research and see if you can find a pro-quality lab in one of the major cities in China that you're visiting. I can ask a friend of mine who is a photographer in Beijing and see if he knows a good lab to recommend.
If you make the mistake of putting your film in checked baggage, a single pass is sufficient to cause damage. How do I know this? I made the mistake of leaving some 4x5 film holders loaded when I checked them in my suitcase. The sheets of film that were closest to the CT-Scan emitter had horrible fogging, with the sheets that were further away were less fogged.
