The semiconducting Cu2ZnSnS4 (CZTS) thin film with high absorption coefficient has long been recognized as a novel solar cell material. In this work, the performances of n-ZnO:Al/i-ZnO/n-CdS/p-CZTS solar cells are analyzed by using semiconductor theory. The influences of doping concentration, thickness, and defect states of CZTS layer and the doping concentration and thickness of CdS layer on the performances of the solar cells and the temperature characteristics are investigated. The calculated results show that the CZTS layer is a main absorption layer in the solar cell. The changes in doping concentration and thickness of CZTS layer have significant influence on the conversion efficiency of the solar cell. The density of defect states in CZTS can sharply degrade the photovoltaic performances. The influences of the doping concentration and thickness of CdS layer can be neglected. The calculated results show that the optimal n-ZnO:Al/i-ZnO/n-CdS/p-CZTS structure has open-circuit voltage of 1.127 V, short circuit current density of 27.39 mA/cm2, fill factor of 87.5%, and conversion efficiency of 27.02%. In addition, the temperature gradient of conversion efficiency is -0.14%/K. These results reveal the promising photovoltaic characteristics of CZTS thin film serving as a solar cell absorber.