Abstract: Taking a three-span prestressed concrete continuous box girder bridge as a research object，a structural health monitoring system for prestressed concrete girder bridges was designed． The monitoring objects，content and design principles of monitoring system was expounded， and the placement of sensors was optimally designed． Based on weigh-in-motion technology，a new monitoring method for the safety of bridge operation were proposed． Using girder bridge dynamic analysis function module of self-developed bridge dynamic analysis software BDANS， the structural dynamic characteristics of girder bridge under random traffic flow was analyzed． The grading prewarning management system of overload vehicles and bridge bearing capacity conditions were respectively established． The real-time monitoring system can monitor bridge continuously，and evaluate bridge safety operation conditions．