In order to study the influence of Duncan-Chang E-B model parameters and their interactions on dam deformation, the global sensitivity of parameters in Duncan-Chang E-B model was studied using the improved response surface method for a homogeneous loess dam. Firstly, five parameters including R f, γ, φ 0, K b and K , which have significant influence on the deformation of earth dam were screened out by fractional factorial design. Then the central composite design in the response surface method was used to conduct further global response surface analysis on the screening results and investigate the influence of parameters and their interaction on the deformation of earth dams. The results show that R f, γ and φ 0 are the three most sensitive parameters to dam displacement, and the interaction between them is also significantly sensitive to dam deformation, which is greater than the sensitivity of a single factor. Therefore, the interaction between the parameters should be considered in similar engineering calculations.