Abstract: The composition of the vermicular cast iron metal matrix was obtained by EDS of the existing cylinder head and phase diagram simulation, which was Fe-xSi-0.6C-0.1Mn-0.05V (x=1.2, 1.5, 1.8, 2.1wt%). The matrix alloys were prepared by vacuum arc melting, and then the treatment of the alloys heated at 930℃for 2 h then cooled in furnace was carried out.The microstructure of the matrix alloys was analyzed and characterized by using XRD, optical microscopy(OM) and SEM. The thermal diffusion coefficients at different temperatures were measured by laser thermal conductivity (TA) to study the effect of Si on the thermal conductivity of the vermicular cast iron matrix. The results show that the metal matrix alloy of the vermicular cast iron is pearlite and ferrite. With the increase of Si content, the content of pearlite decreases gradually, the lattice distortion degree first intensifies and then eases, the thermal diffusion coefficient and thermal conductivity decrease first and then increase, the change of the specific heat capacity is small.When the Si content is 1.8%, the lattice distortion degree is the most severe, the thermal diffusion coefficient and the thermal conductivity are the minimum.With the increase of the temperature, the thermal diffusion coefficient decreases, the specific heat capacity increases, and the thermal conductivity increases, the difference of the matrix alloys with different Si contents decreases.