Abstract: Under the condition of control test,by using the quadratic general spinning　design,the comprehensive effects of N、P fertilizers and water on winter wheat yield were studied.The results showed that the threshold value existed in waterfertilizer　interaction. The threshold value of application amount of N and P_２Ｏ₅ are 90～240 kg／hm² and 56.25～221.25　kg／hm^２ respectively,　and irrigation quota is 1500～3750m³／hm^２.If the application amount of N,P_２Ｏ₅ and water is below the threshold value　respectively, the effect of　N and P_２Ｏ₅ on winter wheat will be unremarkable,and the water use efficiency will be low. Otherwise,the effect of waterfertilizer interaction will be remarkable.It is a significant way for improving the water use efficiency to increase application of N and P fertilizers and limit the water use quantity suitably. A mathematical model of winter wheat yield was established based on the results of experiment and simulation, the optimal scheme of waterfertilizer interaction under various objectives was worked out.