ZnO deposited on sapphire substrate is investigated as a function of growth temperature in the range 350∼650 °C. The surface morphology of ZnO structures changes significantly with increasing growth temperature. Though ZnO crystal quality and optical property can be improved under high growth temperature, ZnO is inclined to form nanostructures. Therefore, we propose the repeated growing and annealing (RGA) growth mode as a reliable and reproducible way for the growth of ZnO film. The RGA growth mode is performed at a growth temperature of 450 °C for 8 min, an anneal temperature of 650 °C for 20 min, and repeatedly switched between growing and annealing. Meanwhile, we compare the effects of annealing under Ar, N2, and O2, and found that a low resistivity of 3.4 × 10-3 V cm and a high mobility of 85.2 cm2 V-1 s-1 can be obtained annealing under N2.