Abstract: The influence of irrigation and supplying phosphorus before sowing on spring wheat yield and Water Use Efficiency(WUE) in typical semi arid area of China in 1996 was tested. The result showed that the close relation between high yield and water use and limited irrigation and manuring phosphorus existed, especially watering was the key factor. On the condition of soil drought extremely before sowing, only watering before sowing and no irrigation through whole growth stage could promote crop to absorb soil water fully, the treatment W(irrigation before sowing) utilized soil water 241.96% more than treatment CK, and yield of the treatment W was 2.76 times of CK, and WUE(on the base of seed) increased 35.62%, comparinig with CK. Under the different soil water contents, the effects of supplying phosphorous were positive. With irrigation, supplying phosphorus contrasting no supplying phosphorus could increase 8.64% and 14.37% in yield and in WUE, respectively. Without irrigation supplying phosphorus could increase 29.79% and 4.77% in yield and in WUE, respectively.