Abstract: The fundamental behavior and physico mechanical property of a typical red clay are studied in this paper,and the contradictory phenomenon that the red clay(laterite) has the unfavorable physical parameters (high water content,high void ratio and high plasticity) as well as relatively good engineering properties such as comparatively high bearing capacity and low compressibility is analyzed and disscussed. Based on the previous test result, a kind of gel cementing structure model for soil mass is presented, and the rationality of the conflicting phenomenon mentioned above for red clay is preliminarily clarified.