Sn4+-doped FeS2 cubes with high yield thin films have been successfully synthesized on FTO glass through a simple hydrothermal process. The Sn4+-doped FeS2 cubes are single crystalline in cubic structure with (200) facet as the main exposed surface. The formation process was investigated. Sn2+ was found to play an important role during the formation process of FeS2 growing on FTO glass. The direct optical band gap value can be estimated to be 1.71eV which is much larger than that of bulk FeS2 due to the Sn4+ doping. The photoelectrochemical properties of the Sn4+-doped FeS2 films were studied as well. There is a significant increase in photocurrent of Sn4+-doped FeS2 electrode compared to that of undoped sample.