Abstract: In this paper, by using the experimental data obtained from Gong County Meteorological Station in Henan Province, the relation between the physiological function of winter wheat in its main stages and soil moisture is simulated, and the optimum index for soil moisture and the drought index for moisture are given. On the basis of these indices, the water consumption of winter wheat in its main stages is obtained from modified Penman equation by consideration of the relative evapotranspiration related to the coefficient of crop leaf area and the index of soil moisture.