At all open exit-entry ports in China, foreign nationals holding valid international travel documents and onward tickets with confirmed seats who intend to transit through China to a third country or region by international flight, ship, or train may remain in China for up to 24 hours without a visa, provided they do not leave the restricted area of the port. However, if they need to leave the restricted area of a port during this time, they must apply for a temporary entry permit from the immigration inspection authority at the port.

Source: National Immigration Administration