Abstract: The law of change in the macro-and-micro properties of cement-soil under NaCl erosion environment is studied through macro-and-micro laboratory tests,and the internal mechanism of the macro shear-properties is analysed.The results show that the microstructure of cement-soil suffered erosion in the erosive course of NaCl,and that the shape and order form of structure units and the development of pore were different under different erosion ages.With the growth of immersion time,the orientation degree and tightness of grain got worse,the number of pore got more and the skeleton structure got looser.The shape-degree,uniform coefficient and Euler number of particle showed decline,and the fractal distribution of particle became ascendent.The change of macro-strength parameters showed "twists and turns,vibration",but ascendent in general.Regressive models for the relations between macro-strength parameters and parameters of microstructure were established through regressive analysis,which improved the study of macro-and-micro properties of cement-soil.