The dependence of dislocation density on various growth conditions for Si MBE films is investigated. Dislocation density is determined by chemical etching and SEM observation. High temperature heat treatment generates dislocations in substrates, and film dislocation density increases with an increase in the substrate dislocation density. The dislocation generation in the substrate is prevented by using a substrate heater designed not to induce thermal stress. The film dislocation density decreases exponentially with an increase in the preheating time of the substrate. The density is proportional to exp (E/kBT) where T is growth temperature. The value of the activation energy is 3.5 eV. Dislocation-free films can be grown reproducibly at 860 °C on (100)-oriented substrates preheated to 1210 °C for 10–20 min.