The grades of drought and flood, the distribution characteristics of precipitation and the temporal and spatial distribution characteristics of drought and flood in the rainy seasons (from May to October) of Hainan province were studied with the methods of Z
-index and empirical orthogonal function (EOF). The results indicate that the precipitation of rainy season in Hainan province is consistent, and after mid-1960s, the change tendency of flood season is from drought to flood. The drought and flood frequently take place in some regions of the west and the north of the province. Further research indicates that there are distinctly contrast areas in the discrepancy fields of previous and same-period circulation. Drought and flood grades in rainy seasons and the previous monthly mean circulation fields exist higher correlation areas, moreover the correlation of the every other season is marked. The stepwise regression equations were obtained with the higher stability correlation factors of the previous monthly circulation fields which were testing. The results show that the prognostic equation using the factor of geopotential height have better fitting and forecast capabilities.