Abstract: The feasibility of simulating precipitation on different temporal scales on Hainan Island using Γ Distribution model was reviewed in this paper. Drought conditions on the island were determined using Standardized Precipitation Index (SPI). The results show that the combination use of SPI with different time scales can be useful in identifying the onset, duration and intensity of different degrees of drought during dry and rainy seasons. It is therefore suggested that 6 and 12 months SPI in winter-spring season and 1 or 3 months SPI in summer-fall season can be used to monitor drought conditions on Hainan Island.