Abstract: In order to study the influence of matrix suction on shear strength of expansive soil in Hefei under different initial dry densities in a large suction range, direct shear tests of expansive soil under different initial dry densities and moisture contents were carried out, the matric suction at shear surfaces of shear specimens was measured by the filter paper method, the influence of dry densities and matric suction on shear strength indexes of expansive soil in Hefei was analyzed. The experimental results showed that dry densities and matric suction had significant effect on the cohesion of the expansive soil, but little effect on the internal friction angles; when the matrix suction value ranged from 0 and 400 kPa, the effect of dry densities on cohesion was great; when the cohesion was over 400 kPa, the effect of dry densities on cohesion was weakened; there was a good linear relationship between cohesion and logarithm of matric suction; the shear strength of expansive soil increased nonlinearly with the increase of matric suction, and the growth rate decreased gradually.