Zinc stannate (Zn2SnO4) films were deposited on MgO (100) substrates by pulsed laser deposition, and Zn2SnO4 monocrystalline films were obtained by postannealing process. The structures, surface morphologies, and optical properties of the Zn2SnO4 films annealed at different temperatures were investigated in detail. Crystal structure analyses showed that the film annealed at 800 degrees C was single crystal Zn2SnO4 with an inverse-spinel structure. The heteroepitaxial mechanism was further clarified by a schematic diagram, and the epitaxial relationships between the film and substrate were Zn2SnO4 (400)||MgO (200) with Zn2SnO4 [001]||MgO [001]. The obtained Zn2SnO4 films exhibited excellent transparency. The optical band gap of the 800 degrees C-annealed Zn2SnO4 film was about 3.97 eV. The extinction coefficients and refractive indexes of the Zn2SnO4 films annealed at different temperatures as a function of wavelength were analyzed in detail.