In order to facilitate the construction of Shannxi Aerospace Industrial Park, a group of Han dynasty tombs were excavated by the Fengxiyuan archaeological team of the Shaanxi Province Archaeological Institute in 2008.A bronze clepsydra was found in pit K4. A lot of information was obtained during the process of conservation, restoration and microscopic observation of the bronze clepsydra.This research helped to control the powdery rust and to uncover some attachments left on the object. What are these attachments? What is the relationship between these attachments and the clepsydra? How did the clepsydra keep time? This article discusses these questions. This research has provided useful information with regard to Western Han dynasty customs, social etiquette, funeral system and the technology available for measuring time.