During the operation of the Three Gorges Project, a large number of retrogressive landslide geological disaster occurred due to the combined effects of reservoir water levels and rainfall, making the retrogressive landslide occupies considerable proportion in reservoir landslide. Through studying formation mechanism of the reservoir retrogressive landslide, according to the deformation and failure mode, the retrogressive landslide is divided into traction district (initial slide district) and passive traction district, and analyzing the interdependence between traction district and passive traction district during the evolution process of retrogressive landslide. For its interaction of mechanical of characteristics, a reasonable physical and mathematical mechanical calculation model is established; and thrust calculation formula of retrogressive landslide is derived preliminarily to provide reasonable design thrust for anti-slide pile design. Taking the Three Gorges Reservoir Area Zhujiadian retrogressive landslide for example, on the premise of determining exist thrust between traction district and passive traction district, by thrust calculation shows that: derivation formula to calculate the design thrust of traction district sliding body is bigger than calculated the design thrust of traction district sliding body separately, compared traction district sliding body and passive traction district sliding body are regarded as the overall sliding body calculation design thrust smaller, it is show that the method of calculating the thrust for anti slide structure design can achieve both safety and economy effect, so as to provide new ideas for the design of retrogressive landslide.