The climate characteristics of thunderstorms at 18 stations in Hainan from 1966 to 2005 are analyzed using the EOF (Empirical Orthogonal Function) method. The results indicate that there was a decreasing tendency in the thunderstorm frequency in Hainan from 1966 to 2005; there occurred less thunderstorms in the south coastal area and more in the north inland areas; thunderstorm days were mainly concentrated in the period from April to October with the peak between May and September; in abnormal thunderstorm years, an obvious negative anomaly existed in low latitude areas at 500 hPa from May to September; the subtropical high is relatively weak and farther east in active thunderstorm years, and vice verse in less active thunderstorm years. Kindex and TTindex are also analyzed,and the results show that they have certain prediction ability for thunderstorms.