The effect of substrate temperature on the grain growth of Cu2ZnSnS4 thin film prepared by co-sputtering of Cu2ZnSnS4and Cu targets is studied. The chemical composition, morphology and band gap of Cu2ZnSnS4 thin films are characterized by Raman, energy dispersive spectrometer（EDS）, scanning electron on icroscope (SEM) and UV -Vis-NIR spectrometer, respectively. The results show that the formation of Cu2ZnSnS4 thin film follows different mechanisms. When the substrate is under room temperature, the growth of Cu2ZnSnS4 grains follows the two-step mechanism, leading to the inhomogeneous distributions of particles and element of Cu2ZnSnS4 thin film. However, Cu2ZnSnS4 grains appear during the co-sputtering process in Cu-Zn-Sn-S precursor at substrate temperature from 120—200 ℃, which act as nucleation seeds to promote the growth and homogeneous distribution of Cu2ZnSnS4 grains in the post sulfurization process. With increasing substrate temperature, the crystallinity of Cu-Zn-Sn-S precursor and Cu2ZnSnS4 thin film becomes better, and the band gap of Cu2ZnSnS4 thin films first increases then decreases to 1.55 eV.