Abstract: This paper studies the impact properties of saturated sand under drained and un -drained triaxial conditions as well as the reconsolidation features. The results indicate that under the undrained impact, the pore water pressure springs up in an accumulative way and then becomes stable. The axial strain grows with blow counts and the maximum axial deformation increases with impact energy both in a linear way. The volumtric change is generated during the process of reconsolidation; whereas, under the drained impact, the pore water pressure in the process of impact would also spring but not accumulate. The relationship between axial strain and the blow count as well as the maximum axial deformation and impact energy resembles the hyperbolic curves. The volumtric change basically grow out of the phase of impacting. By comparison, it revealed that the axial deformation without draining is larger than that with draining under the same impacting energy and the same blow count, while the total volumtric change with draining will be larger than that without draining.