Abstract： Collision cascades of 1 keV/atom gold clusters and 0. 2 keV/atom aluminum clusters impacting on gold targets have been investigated by moleculardynamics simulation. The spectra of gold recoil atoms are broader for cluster bombardment. The maximum recoil energies are nearly 2? times higher than the kinematic limit of mono-atomic bombardment. The multiple hits and the collisions between moving atoms make the recoil energies of target atoms increase. The energy transfer between two moving atoms are studied by conservation laws.