Abstract: Parameters of rockmass of Suofengying Hydraulic Power Plant were derived from displacement back analysis based on the support vector machine and simulated annealing.Firstly the support vector machine was used to substitute the time-consuming finite element analysis,and secondly the simulated annealing was used for the optimization of objective function to avoid that the search fell in one of the minimums and could not go any further when the conventional mathematical optimization methods were employed.The displacement calculated by FEM with parameters obtained from back analysis was close to the measured value.