Abstract: To investigate the dynamic deformation characteristics of light weight soil mixed with EPS particles, the influences of different mixed ratios and confining pressures on the backbone curve and the parameters of Hardin-Drnevich model for light weight soil are studied through the dynamic triaxial tests, and the modified Hardin-Drnevich model is established and verified. The results show that the backbone curve of light weight soil exhibits obvious nonlinear and strain-hardening characteristics. The relationship between reciprocal of dynamic shear modulus and shear strain of light weight soil increases linearly, indicating that the dynamic deformation characteristics of light weight soil can be described by the Hardin-Drnevich model. The reciprocal of the maximum dynamic shear modulus and that of the maximum dynamic shear stress decrease with the increase of confining pressure and cement content, and increase with the increase of volume ratio of EPS particles. On the basis of the Hardin formula, the expression for model parameters is proposed by introducing the relative structure k and the generalized pore ratio e', and the modified Hardin-Drnevich model is established. By changing the stress state and stress path, the relative error between the calculated value and the test value is less than 11%. The predicted results by the modified Hardin-Drnevich model for the backbone curves of light weight soil are good, which shows that the modified Hardin-Drnevich model can describe the dynamic response of the special structure of light weight soil under complex stress conditions.