With 4-factor quadratic regression general rotation design, the effects of irrigation, nitrogen, phosphorus and potassium fertilizers on yield of processing potato were studied and the corresponding regression model were obtained. The results showed that: the effect of the four factors on potato yield was in an order of irrigation＞N＞K＞P. There was interaction between the four factors. The maximum yield of processing potato simulated by computer was 46.75 t/hm2, corresponding to irrigated water, N, P, K fertilizer usages of 2 520 m3/hm2, 457.5 kg/hm2, 825.0 kg/hm2 and 247.5 kg/hm2. The optimal selection model from nitrogen, phosphorus and potassium ratio of the highest yield, fertilizer costs, fertilizer profits, investment efficiency of fertilizer were 0.86 × 104 Yuan/hm2, 1.88 × 104 Yuan/hm2 and 2.19 Yuan/Yuan.