Abstract: In recent years, the response equation of quadratic surface is adopted to reflect the production function relationship between N, P fertilizer input and yeild in the research of proper application of fertilizers. The analysis from the results of muliple-spot experiments indicated that all the quadratic equations could objectively reflect the actual situation of each spot and the degree of imitative coincidence is good. But many facors should be considered when the method is used in field.This paper intends to approach the following problems for the field experiment of winter wheat under the condition of similar weather and single soil type, the relationship between the linear entry in equations with the livel of the initial nutrient value in soil; the relationship between coefficients of linear and quadric entries in the response equation; the effect of soil nutrient N, P ratio on their interaction and application response; and yield estimate on the basis of soil productivity and cost of fertilizer application recommanded by the response equation.