Abstract: According to the observed data of water consumption (E) of the main crops in the prefectures of Shijiazhuang, Xinxiang and Dezhou and in Beijing, evapotranspiration coeffcient of crops (a) in Penman's formula is determined by calculating evaporativity from the water surface (E₀) :a=0.78 for winter wheat, a=0.72 for cotton and a=0.78 for corn. A formula, E=aE₀, is adopted to estimate water consumption of the crops in their growing pariod in the low plain of Hebei province. The estimated water consumption is as follows; 400-470 nim for wheat;613-708 mm for cotton and 350-405 mm for corn.In successive rotation of wheat and corn, an annual amount of water deficit in wheat field is about 242 mm, while in monoculturellt, It is reduced approximately to 164 mm. water deficit for one-crop farming of cotton and corn amounts to 107 mm and 39 mm respectively.water deficit for winter wheat in Cangzhou and the eastern part of Lang-fang exceeds 180 mm, while it is decreased to less than 140 mm in Handan and southern Xingtai. The areas seriously suffered from water shortage are located in southern Changzhou and the western part of Xintai and Hengshui. As for the areas of Wenan Dacheng and Qingxian Counties, water deficit becomes less serious.From April to May is a period of the highest water consumption of wheat and the sowing time of cotton and other spring sowing crops. But in this period precipitation is the lowest. Therefore, a complementary amount of water is required in irrigation.