Abstract: Stress-path triaxial tests of sand samples were conducted under constant deviatoric stress with low speed cyclic loading and unloading of spherical stress to study deformation mechanism of saturated sand with two different initial relative densities. Influences of initial relative density on volumetric strain and shear strain were examined, and the following results are obtained: (1) volumetric strain and shear strain are accumulated obviously as the number of cycle increases; (2) when consolidation deviatoric stress is small, accumulative volumetric strain decreases and accumulative shear strain increases with the increasing initial relative density, but it has no effects on cyclic volumetric stain or shear strain; (3) when it is large, these accumulative strains and cyclic volumetric and shear strains all decrease considerably with the increasing initial relative density. With the number of cycles increasing, the effects of initial relative density on cyclic shear strain decrease gradually, and even disappear.