Donghai bridge is a linkage connecting Luchao Port in Shanghai and Yangshan Island deep Water Port. The linkage is about 32km long and consists of 2 cable stayed bridges and a large number of spans of eontinuous and simply supported bridges. It crosses East China Sea and lies on soft clay so the durability gainst ocean environment and the un-uniform settlement of foundations are concerned. The bridges are under construction and are planed to open to traffics around the end of 2005. A structural health monitoring system designed and is being installed to the bridge. This paper reported the conceptual design and the key issues thpse have been studed on the structural health momtonng system of the bridge.