Evapotranspiration is the most important output in the land hydrological cycle.However,evapotranspiration estimation is still an intractable problem especially in mountainous areas To explore the water cycle in mountain region,different evaporation experiments for ground and water surface were carried out in eastern slope of the Gongga Mountain,southwestrn China.The Penman-Monteith formula was spplied to simulate the dynamic ofevapotranspiration for naked land,Abies forest and shrub-grass areas The simulating results show that the net radiation air temperature and vegetation types are the predominant factors to control the dynamic of evapo-transpiration,air temperature and vegetation types are the predominant facrtors to control the dynamic of evapo-transpiration The evapotranspiration process modeled for naked land is similar to observed evaporation of water surface The simulated values of evapotranspiration of forest and shrub-grass areas are higher in growth period,or lower in non-growth period than that of naked land surface The difference of them for these tow kinds of land sruface varies from-25%to25%,The modeled results show that the modified Penman-Monteith formula can be used satisfactorily in the hydrological cycle analysis for mountain region with forest coverage.