Abstract: This paper attempts to develop a method to back-analyze the constitutive parameters for Duncan-Chang E-B model, based on in-situ pressuremeter tests. The main work includes:①the working mechanics of pressuremeter test is numerically simulated with finite element method, in which Duncan-Chang E-B model is applied;②a practical back-analysis method and computing program of constitutive parameters for Duncan-Chang E-B model are developed, based on the non-linear optimization theory with damping least squares;③some measured pressuremeter curves are back-analyzed with the method to determinate Duncan-Chang E-B model parameters for the foundation soil of some practical project, based on sensitivity analysis of parameters and laboratory tests, and the calculated results are proved practically significant.