Ancient timepieces are combinative products of science and technology, and they were communicated to China through importation during the 17 to 19 centuries. Clocks collected by Chinese emperors are elegant works and show the highest manufacture level. Regarding the gravity-driven clocks, the methods to apply gravity as a power source are ingenious. The development of power sources in timepieces and the communication of technology from Europe to China are introduced briefly. Four typical gravitydriven clocks are presented and divided into two types, driven by an outer force and by its own weight. Furthermore, structural analyses regarding the mechanisms of typical gravity-driven clocks are provided.