Abstract: In Taian City of Shandong Province,the retaining wall of Gaoyupu Cross Bridge on No.205 National Highway is located on an unstable slope subjected to double dynamic loading,one is the vehicles running on the highway on the top of the slope,and the other is the train trucks acting on the bottom of the slope. On this condition,the whole slope and retaining wall lose their stability,which threatens the railway,and half range of the road was interrupted. According to characteristic of this engineering disaster,it is deeply studied the mechanism of the retaining wall instability and its reinforcing scheme,and good effect are obtained