Reviewing the investigation history of slope-sliding forecast,the author analyzed the characteristic of nonlinear dynamics in the process of slope-sliding displacement primarily and gave out formulas for the displacement,velocity and acceleration of slope-sliding blocks with intraducing the transmission method of unbalanced thrust into the analytic method of dynamics in the process of slope-sliding displacement.This method presented the criteria for the acceleration of failure by slope-sliding and was able to do inverse computation of parameters of machanics on slide surface.