Voltage is no problem with Apple plugs. The only issue might be if you have the three-prong US plug. Major hotels will have an outlet to accept three-prong US plugs, but otherwise you might want either a "cheat" adapter that accepts the three-prong and has a two-prong (flat or round) plug for the Chinese outlet, or else get an adapter that accepts your three-prong and plugs into the left illustration from anacapamalibu. Both adapters should be easily available in China, but would save time to get before you travel.