We report on the successful fabrication of single-phase polycrystalline BaSi2 films on Si(111) substrates by a simple vacuum evaporation method using BaSi2 granules. Substrate heating was found to be the key, and high substrate temperatures are required to realize single-phase BaSi2. The underlying mechanism is discussed considering the composition of vapor flux, and we confirmed that the vapor flux is Ba-rich at the initial stage of evaporation. The reevaporation of excess Ba atoms or their reaction with Si substrates would be responsible for the realization of stoichiometric single-phase BaSi2, which explains why high substrate temperatures are necessary.