In addition to the error influence of soil constitutive model, the material parameters reasonable or not are also one of the key factors affecting the prediction accuracy in stress and deformation control numerical simulation of high core rockfill dam. The traditional parameter back analysis methods do not consider the influence of correlation between material parameters which exist problems of parameter values may not match with the actual material properties; complicated geological conditions and many back analysis parameters make high computational burden. Therefore, according to Duncan-Chang E-B model parameters, through statistical analysis of a large number of experimental data, the calculation results show that the shear strength parameters △φ and φ, tangent modulus coefficient Ke and bulk modulus coefficient Kb, tangent modulus index n and m are significantly related by regression equations; then the basic model parameters φ, Rf, Ke and n are determined for back analysis. The response surface equation of basic back analysis parameters and calculated displacement values is established; and then the parameters optimum solution is obtained by using improved genetic algorithm and the known parameter regression equations. The Duncan-Chang model parameters are calculated by the combination of Pubugou Gravel Soil Core Rockfill Dam. The results show that the calculating parameters are more in line with the real characteristics of materials if considering the parameters correlation; the number of back analysis parameters decreases by 7, which can effectively improve the calculation efficiency; this method can be used as a reference for similar projects and has significant engineering application value.