Abstract: This paper analyzed the character of water consumption for C₃-plants (wheat and soybean) and C₄-plants (millet and maize) and found that the process of water consumption intensity is very different for the two types of plants.C₃-plants possess wide peak value zone, but C₄-plants narrow one.The width or narrow of peak value zone of the water consumption can probably cause the difference of water consumption between C₃-plants and C₄-plants.The ratio of the water consumption by crops to evaporation from water surface in the growth stages can be regarded as a curve of physiological water consumption, from which it is seen that the water consumption in the beginning and the end o.f growth is small,but in the middle of growth it is large.For winter wheat the peak value zone of water consumption is in tillering and florescence-grouting, for soybean in florescence-bearing fruit, for millet in florescence-grouting, for maize in heading-grouting.The detemination of the peak value zone has an importance in irrigation.In North China Plain, the key periods of water consumption by crops usually are in April-May and July-September.Water supply in these periods is more important.Characteristic coefficient of water consumption by crops is quite different,for example, the coefficient for soybean is about twice as high as the coefficient for millet.It must be on the basis of the strict experimental data to obtin the coefficient of crops.It must consider plant types and water consumption coefficient to estimate evapotranspiration from agricultural lands.