Abstract: In view of complex nonlinear relationship between dam mechanical parameters and dam displacements,the least squares support vector machine was applied to the back analysis of displacements of dam mechanical parameters.Firstly,the training samples of the least squares support vector machine were obtained by the finite element model,and the complex nonlinear relationship between relative values of water pressure components of dam displacements and mechanical parameters was established.At the same time,actual relative values of water pressure components were isolated from the measured dam displacements by using the partial least squares regression,which were inputted into the least squares support vector machine model,and the values of back analysis of the dam mechanical parameters could be obtained.A concrete gravity arch dam was taken as an example,and the least squares support vector machine was applied to the back analysis of dam elastic modulus,rock deformation modulus and elastic modulus of main faults.Though comparative analysis,it is found that the method is feasible.