The climate characteristics of the occurrence frequency of abnormal high temperature from May to July in Hainan were analyzed, and their influential factors,sea temperature over the South China Sea and the Northern Hemisphere 500 hPa height field,were analyzed. It is indicated that the occurrence frequency of abnormal high temperature had a 3.8-year period in May, but a 5-year period in June; the sea area around the middle South China Sea was the key area influencing the frequency of abnormal high temperature in the corresponding periods. In the abnormal year, the circulation characteristics over the Eurasia Continent at the 500 hPa were the blocking high in the middle latitudes, the southward westerly trough, and the subtropical high over the western Pacific Ocean inclined westward and southward for a long time.