Abstract: The evolution laws of dynamic shear modulus and damping ratio of the compound soil mixed by the arsenic sandstone and the Fujian standard sand along with dynamic shear strain are studied by using the GDS dynamic triaxial apparatus for soils.A logarithmic attenuation model for dynamic shear modulus ratio and a logarithmic growth model for damping ratio are proposed.The relationship between the model parameters and the mass ratio and water content of the compound soil is discussed by normalizing the test data.The dynamic stress amplitudes of the composite soil with different mass ratios and water contents reaching the failure dynamic strain are compared, and the mass ratio corresponding to the maximum dynamic strength is determined so as to provide a theoretical basis for the treatment of desert roadbed by the composite soil.The results show that the dynamic constitutive relation for the composite soil of arsenic sandstone and sand can be described by the hyperbolic model, and the model parameters are related to its mass ratio and water content.When the water content is constant, the optimal mass ratio of arsenic sandstone to sand is about 7∶3.When the mass ratio is constant, the model parameters M and N of the attenuation model for the dynamic shear modulus ratio the composite soil decrease with the increase of the water content.The model parameter P of the growth model for the damping ratio increases with the increase of the water content, and the parameter Q decreases with the increase of the water content.The mass ratio and water content of the compound soil have significant influences on its dynamic characteristics.