Abstract: On the basis of meteorological and hydrological data in seven catchments in Yunnan Province,three formulae Eqs.(3),(5),(6) calculating the evaporation from land surface are tested and compared.It is found that Fuh's formulaEqs.(6) is the best one among them.A new parameter U,undulation of topography Eqs.(10),is defined.By virtue of Fuh's formula and the undulation of topography,the evaporation from land surface in the mountainous country can be calculated without much error.