Penman formula was used to calculate the evapotranspiration in the upper valley of the Huanghe river since 1980.The variation tendency of some climatic factors,such as evapotranspiration,sunshine duration,air temperature,air saturation deficit and etc,were analysed.The dry climate impact on the evapotranspiration in the area was focused in the study.The results show that the evapotranspiration is increasing annually with the speed of 3.25 mm in the area;while the sunshine duration which is considered as main impact factor,is increasing with 3.6 hour/year;air temperature is appearing the increasing tendency,and its climatic tendency is 0.4℃/10 years;air saturation deficit is increasing with 0.02/year.Therefore,It is suggested that the evapotranspiration is greatly increasing as increment of sunshine duration,air temperature and air saturation deficit in the area.But the increment of evapotranspiration and decrement of precipitation amount impact directly on the decrement of flow curve and expanding of grassland′s desertization in the upper valley of the Huanghe river.