According to the Customs Law of the People's Republic of China and PRC Customs' Supervision and Management on Inward and Outward Passengers' Luggage, the baggage carried by inward and outward passengers shall enter or leave the territory where Customs office is available, and must be declared to Customs officers as obligated.

Unless otherwise specified by laws and regulations, no luggage carried by both inwards and outwards passengers shall be exempt from inspection and release by China Customs. Customs inspection of luggage is based on the principle of "clearing articles of reasonable quantity for personal use only". Different types of luggage carried by passengers shall be subject to different limit and amount for levying and exemption of duties.

In the event passengers are carrying articles that require declaration to the Customs for entry or exit, the passengers should submit a form entitled "Declaration on PRC Customs Inward and Outward Passengers' Luggage" or Customs declaration documents at the declaration desk, such that they truthfully declare the luggage as required, and submit them to the Customs. In a double-channel Customs office, the above-mentioned passengers shall choose the channel of "declaration" (e.g. "red channel") for clearance and passengers who carry articles which do not require customs declaration shall choose the channel of "non-declaration" (e.g. "green channel") for clearance.

Please note, declaration documents proving Customs' inspection and signature must be kept safe, in case needed for return or after entry.

Luggage carrying a Customs seal must not be unpacked. Likewise Customs seal affixed to luggage must not be damaged or broken. In doing so, the passenger may be charged under the Laws of China.

Source: english.gov.cn