Abstract:the study of long span cable-stayed bridge seismic performance only takes main bridge as analysis object. There are few reports about the research of earthquake impact between cable-stayed bridge and approach-bridge. Take a Jiu-Jiang big bridge as example, the impact analysis model between cable-bridge and approach-bridge was built. The analysis about impact influence factors between cable-stayed bridge and approach-bridge was systematically studied. The influence factors include site-type, high of gravity center, approach-bridge structure form. Some significant conclusions are got. It can be taken as references for similar projects seismic designing.