According to Moore-Coulomb strength theory, combined with the shear strength reduction method, assumed that the exerted value of the soil’s internal friction Angle and displacement were in nonlinear, and the exerted value of the soil’s cohesion and displacement were in linear, and then put forward a unified, continuous with displacement earth pressure calculation model, and this model could be used to calculate the active and passive earth pressure for cohesive soils and cohesionless soils in any nonlimited state and any movement mode. Through the analysis of the calculation model showed that: (1) The above assumptions were all reasonable from the two perspectives of the theoretical and the measuring; (2) The variation process of earth pressure acted on the retaining wall with displacement, could regard as the process of the soil’s shear strength parameters exerting gradually; (3) Given the physical meanings to the calculated parameters; (4) Analyzed the characteristics of the calculation model, and pointed out that there were calculation errors when the displacement of retaining wall was in (0, x0H) for the Rankine earth pressure theory.