Cu2ZnSnS4 (CZTS) thin films are prepared by the step sputtering with three binary-sulfide compound targets of ZnS, SnS, CuS. The annealing is carried out at different temperatures. The influences of annealing temperature on crystal structure, element composition, surface morphology and optical characteristics of CZTS thin films are investigated. The results show that the secondary phases like Cu2S and SnS are found in the CZTS thin films at the annealing temperature of 400 ℃. With the increase of the annealing temperature, the variety of the secondary phases decreases. When the annealing temperature is 550 ℃, the thin film surface is smooth and compact and the variety of the secondary phases is the least. However, when the annealing temperature is 600 ℃, the film surface becomes rough and the variety of the secondary phases increases.