Abstract: In order to research the correlation degree of the physical property indexes of mudstone with compression deformation parameters and shear strength parameters respectively in Nanning, Guangxi, the improved index weight calculation method in grey correlation method was used to find out the primary and secondary factors affecting compression modulus E_s1-2, cohesion с and internal friction angle φ. The results indicate that water content ratio ω and porosity ratio e are less related to compression modulus E_S1-2, the order of the contribution rate of the other four physical property indexes from large to small is natural gravity γ, saturation S_r, liquid limit W_L and plastic limit W_P. Natural gravity γ, saturation S_r and liquid limit W_L have little influence on the mechanical parameters of cohesion c and internal friction angle φ, the order of the contribution rate of the other three physical property indexes from large to small is water content ω, plastic limit W_P, porosity ratio e and water content ω, porosity ratio e, plastic limit W_P. Based on the conclusions drawn, it can play a reference role in the design calculation of mudstone engineering.