Abstract: This paper andyzes the trends of 20 cm pan evaporation over the Yangtze River basin from 1951 to 2000 using Mann-Kendall trend test and IDW interpolation methods.The significant negative trends of annual,summer and autumn pan evaporation characterize the trends of pan evaporation since 1951,especially in the 1990s. The annual and summer pan evaporation in the 1990s is the lowest for the recent 50 years;the annual and summer pan evaporation anomalies in the 1990s are -25.9 mm and -36.1 mm,respectively. But this trend is much more significant in the middle and lower reaches than that in the upper reaches in the Yangtze River basin,especially in the Poyanghu basin.