Abstract:The calculation method of equivalent modulus of elasticity of foundation is studied in the principle of displacement equivalence by elastic multi-layer theory, and the boundary conditions are identified and studied based on the analysis of the influence factors for the calculation method of equivalent modulus. The deficiencies in the present calculation methods of equivalent modulus of elasticity of foundation are analyzed. Based on the analysis of great amount of computing data, the calculation expressions are reestablished when the load radius is 15 cm, which has better precision and extension, besides, the modified coefficient of load radius is added. The calculation expressions of equivalent modulus of elasticity of foundation are applicable to the calculation when the ratio of equivalent base modulus to subgrade modulus is greater than 2 and base equivalent thickness is greater than 20cm, and the load radius ranges from 10 cm to 50 cm.