Abstract: This paper uses the results of standard soil triaxial tests to examine the structural and impaction factor of Xiashu soil in Nanjing. The results show that the Xiashu soil evidently has structures. . Before the yield strain, the structural strength of the soil quickly is developed. After the yield strain, the soil structure is broken. When every structural unit is re-arranged to form a stable structure, the original soil structure is totally destroyed. The impaction factors are confining pressure and moisture content. The result shows that the structure strength does not vary with the change of the confining pressure. A power function is found for the relationship between the structure strength and the moisture content. At last, the paper discusses the possibility of using structure strength to replace the matrix suction strength.