The Monte Carlo program TCIS simulating the transport of energetic ions and atomic collision cascades in solids has been used to investigate some problems on physical sputtering. Atomic collisions at the region of low energies contribute to the most of the sputtering yield. At low energies, the time integral τ of the atomic collision calculation will not be a negligible quantity. In this paper, the influence of τ on sputtering yield is studied. The main features of the Monte Carlo code are introduced. Some results of computation concerning sputtering are given. The information about physical sputtering at atomistic level can be obtained by this code,which are useful in the research of sputtering mechanism.