In this study, polycrystalline thin films of 330 nm in thickness with different SnSe and SnSe2 contents were prepared by co-evaporation of Sn and Se through adjusting source temperatures and substrate temperature. The result illustrates that the film with pure SnSe phase is p-type and consists by bulk-like nanoparticles, its resistivity is high up to 139 m Omega.m, which results in a low thermoelectric performance. The films with the coexistence of SnSe and SnSe2 phases are comprised of nanosheets. The existence of SnSe2 phase changes the conductivity type of the films to n-type and reduces resistivity. M the same time, the nanosheets perpendicular to the substrate can improve the Seebeck coefficient by filtering the low energy carrier. When the SnSe2 phase content is 34%, the Seebeck coefficient and the power factor of the film can reach the maximum, 255 mu V/K and 155 mu W/(m.K-2) at 250 degrees C, respectively.