Abstract: With the change in vehicle loading, the load amplitude will also change. However, most of the existing studies focused on the dynamic characteristics of cement soil under the constant dynamic loading, and the dynamic characteristics of cement soil under staged cyclic loading were seldom examined. Using the GDS dynamic triaxial apparatus, a series of dynamic triaxial tests of cement soil are carried out to investigate the influence of static deviator stress and confining stress on the dynamic characteristics of cement soil. The results show that the axial plastic strain of cement soil increases with the increasing confining stress and static deviator stress ratio. The axial strain of cement soil is in the range of 0.1%～0.5%, and its strain development belongs to a stable type. The staged loading and unloading have a great influence on the development process of the plastic strain of the cement soil, but have little influence on the ultimate strains. The empirical model of plastic strain considering loading and unloading conditions, confining stress and static deviator stress ratio is established. The correlation coefficient of staged unloading is greater than 0.95, while that of staged loading is between 0.8 and 0.9. The results show that the first stage load plays a leading role in the strain development, while the maximum dynamic stress ratio cannot dominate the strain development when the first stage load is small. Under the condition of staged loading and unloading, the backbone curve of the cement soil shows two modes: ascending type and descending type, which can be simplified as a multi-segment straight line. Based on the established cumulative plastic strain calculation method, a method to determine the dividing point of the multi segment straight line is proposed, and its feasibility is also verified. The research results lay a foundation for systematic analyses of the dynamic mechanical properties of cement soil under traffic loading.