Abstract: Based on the growing period data of early hybrid rice in the last 22 years,the causes of low yield of early hybrid rice in Hainan Province were analyzed by relative survey method.The result showed that the primary factors of yield reduction were low temperature and less sunshine in rice shooting stage.The correlative coefficient and multi-coefficient between increase rate and cloudy days and mean temperature of shoots were 0.6094 and 0.4799 and 0.6098 at 0.01and 0.05 and 0.05 significant level respectively.Considering early rice,late rice and winter vegetable production chose the optimal sowing date.

Key words: Hybrid early rice, Hybrid early rice, Yield decrease, Low temperature and less sunshine, Optimal sowing date