Based on the meteorological data collected from 616 weather stations in China during 1975—2004,daily,monthly and annual reference crop evapotranspiration(E_T0) were calculated by using the Penman-Monteith equation recommended by FAO.As for the long range annual averages,E_T0 ranged from 800 to 1100mm,with the maximum in Northwest China and the minimum in Northeast China.For temporal variation,it reached the maximum value in 1978 and the minimum in 1993.The inter-annual fluctuations were small in the east of the Qinghai-Tibet Plateau and Notheast China and large in Northwest China.The annual variability varied between-30—30mm·(10yr)^-1,dramatically declining in Western China and the Yangtze River basin,and rising in the East coastal area,the middle and upper reaches of the Huanghe River and Northeast China.Main factors leading to the temporal trend of E_T0 declining-first-then-rising were sunshine duration and saturation deficit.