Abstract: The deterioration mechanism and mechanical properties of site soil, a multi-component material with complex material composition and internal structural characteristics, have attracted much attention. Based on the idea of material analogy and generalized similarity theory, this paper explores the determination method of mechanical properties of inter granular cement in site soil at meso scale. According to the electron microscope and a small amount of mechanical test results of site soil, a meso model composed of particles, cement and pores is developed, and the stress-strain relationship formula of site soil with different water content is deduced. The numerical results are in good agreement with the macro test results, which shows that the present concepts and methods on site soil in this paper are feasible.