The mechanical properties of sandwich composites play an important role in its applications. In this paper, the impact response and damage evolution process of sandwich composites under low velocity impact are studied experimentally and numerically. From the experiment, the dynamic responses of the load and velocity variations under different impact energies are observed and the damaged area is measured through C-scan technic. In the numerical simulation, the plastic behavior of foam core and the damage behavior of composite face sheet are considered. So the damage mechanism can be clearly figured out. The influences of the damage attenuation parameters and its decay algorithm of composite face sheet are investigated. The critical impact energy can be estimated numerically and a linear relationship between the indentation depth and the impact energy is found.