Monthly and annually wind speed data from nine meteorological stations over Heihe River Basin, observed by the China Meteorological Administration from 1960to 2009,were used to analyze the spatial and temporal variability of average wind speed.Mann-Kendall methods,inverse distance weighted(IDW),and correlation analysis were employed.The result showed a decreasing trend in annual average wind speed during the past 50years,and theβvalue was-0.01.Decreasing tendency in wind speed occurred in four seasons(spring,summer,autumn and winter)as well,and theβvalues were-0.012,-0.011,-0.007 and-0.008,respectively.Interdecadal change of wind speed in the 1960sand 1970sshowed positive anomalies,while a negative anomaly was showed since 1980s.The intra-annual variation of wind speed appeared as partial bimodal.Meanwhile,these two peaks existed in April and November,respectively,and the first peak was much larger than the second one.Spatially,slightly increasing trend was showed in the upper reaches with an average rate of 0.01m/s,while decreasing trend were showed in the middle and lower reaches with an average rate of 0.005and0.029m/s,respectively.At the same time,the trends in different regions varied significantly in four seasons.Abrupt change in annual wind speed occurred in 1985,while abrupt change in four different seasons occurred in 1986,1984,1983and 1985,respectively.Decreasing trend in annual and spring wind speed was correlated with average temperature,average maximum temperature,average minimum temperature and potential evapotranspiration,but this correlation declined in summer and autumn.Only potential evapotranspiration in winter affected wind speed significantly at the 0.01level.All this indicated that,decreased wind speeds was the main factor that leading to the decrease of potential evapotranspiration in Heihe River Basin in recent 50years.