Abstract: According to the ecological appropriate theory, the logarithm normal distribution model between the growth of natural vegetation and the depth of groundwater was established.Based on the model, the quantitative method for ecological water requirement of natural vegetation in arid area is proposed, by using the remote sensing technique to divide the area in the light of different ecological vegetation and the spot tested data of vegetative physiology demand.As an example, the ecological water requirement of natural vegetation in Heihe River basin is computed. Compared with the other related researches, the result is rational.The method is reasonable and can be used in other arid area.