Abstract: The paper aims to explore the relationship between ET0 and climate change in Yunnan for enhancing forecast accuracy of drought occurrence. Based on data of 52 meteorological stations in Yunnan from 1981 to 2011, the causes for ET0 change were analyzed by using sensitivity coefficient and the contribution rate, with the ET0 estimated by Penman-Monteith equation, including the annual ET0 (ET0,y) and the yearly ET0 of four seasons (ET0,w, ET0,s, ET0,e, ET0,u). The results showed that: (1) the order of sensitivity degree of ET0 in Yunnan to climatic factors was: the average temperature＞relative humidity＞sunshine hours＞wind speed; though the relative humidity was a high sensitive factor, its impact on ET0 was lower than average temperature and sunshine hours; (2) the leading factor of ET0 change in Yunnan had periodicity; the decreasing sunshine hours was the main factor leading to the decrease of ET0,y in 1981-1990, and in 1991-2011 the rising of average temperature was the leading factor of the ET0,y increase; (3) the leading factor of ET0 change in Yunnan had the seasonal characteristics; in 1981-1990, the leading factor of the increase of ET0,w in winter was the average temperature, and the leading factor of the other three seasons was the sunshine hours which led to their ET0 decrease; in 1991- 2011, the rising of average temperature was the dominating factor leading to the increase of ET0,w and ET0,u, and the leading factor of both the decrease of ET0,s and the increase of ET0,e was sunshine hours.