You must obtain a visa prior to arrival, and have a passport with at least six months’ validity remaining. The lack of either will result in a fine and immediate deportation.
U.S. citizens traveling to China can apply for a ten-year multiple-entry visa, useful for repeated travel or trips to Hong Kong or Macau with returns to China. This visa may be in an expired passport if the traveler also carries a valid passport.
You must also have a valid visa to exit China and you must leave China before the expiration of the listed duration of stay. If you overstay in China, you may be detained and fined. If your visa has expired or will expire before you can depart China, you must apply for a visa extension from the Entry/Exit Bureau before attempting to leave the country. Requests for extensions from the Entry/Exit Bureau can take some time and may not be expedited to meet your travel needs.
Visit the website of the Embassy of the People’s Republic of China for current visa information.
The Tibet Autonomous Region (TAR), requires special permits for tourist travel, usually obtained through a Chinese travel agent. If you do enter a restricted area without the requisite permit, you could be fined, taken into custody, and deported for illegal entry. To learn more about specific entry requirements for Tibet or other restricted areas, check with the Embassy of the People’s Republic of China.