Abstract: In order to find out the relationship between the yield of asparagus and the amount of nitrogen phosphorus potassium fertilizer, a pot experiment was done, in which the authors adopted the optimum design method of the tri-factor quadratic saturation D and made a preliminary research on the optimum fertilizer structure for the biennial asparagus. By analysis, a mathematic model of the relationship between the growth index of the biennial asparagus and the amount of nitrogen phosphorus potassium fertilizer was established. By the model, the authors clarified the relationship between the main factor effect, the single factor effect, the marginal effect, the interaction effect and the biennial asparagus growth index. Under the conditions of this experiment, the optimum quantity of fertilizer in the first year was pure nitrogen 425.595 kg/hm², P₂O₅ 290.595 kg/hm², and K₂O 116.325 kg/hm².