ZnS films grown on (100) Si substrates were successfully obtained by molecular beam epitaxy. The dependence of the crystal quality on growth conditions was studied. The substrate temperature ( T s) and the molecular beam flux ration of Zn to S ( J Zn/ J S affect the crystal quality and the growth rate of the ZnS films profoundly. Crystallographic quality and surface morphology were significantly improved by growing at temperatures higher than 300°C. Below 300°C, growth orientation and growing planes of ZnS are different from others, namely ZnS(111) ‖ Si(511). The films grown at higher T s ( > 300°C) have the relation of ZnS(100) ‖ Si(100). By increasing J Zn/ J S, the surface morphology became worse. It is found that the optimum growth conditions are T s = 340° Cand J Zn/ J S =1 or 2. The growth rate of ZnS decreases with incresing T s , and increases with increasing J Zn/ J S and t hen saturates above J Zn/ J S = 3. From these results, it is presumable that ZnS growth is controlled by the sticking coefficient of the minority molecular species.