Abstract: Dynamic characteristics between the cable-stayed bridge and the approach-bridge are different.It the out-of-phase vibrations may happen under horizontal earthquake effect.Then lead to collision response,cause expansion joint damage and beam collapse.Aiming at the research on the collision problem between the big span cable-stayed bridge and approach span is not overall deeply,the anti-collision measures study between cable-stayed bridge and approach span is not systematical enough,The unseating prevention devices shock absorption effect on the collision of cable-stayed bridge and approach span is researched,the influence law of unseating prevention devices on the collision of cable-stayed bridge and approach span is analyzed systematically.The results show that unseating prevention devices can reduce the relative displacement of adjacent beams and collision force peak.Unseating prevention devices are perfect prevent collision measure between cable-stayed bridge and approach span,But the influence of approach span's displacement and approach span fixed pier seismic requirements are rather complex.