Abstract:The effect functions of nitrogen, phosphorus and potassium application codes on the yield and total platycodin of Platycodon grandiflorum were established by conducting field experiments using three-factor D-saturation optimal design (310). The results show that the effects of nitrogen, phosphorus, and potassium on yield and total platycodin are nitrogen > potassium > phosphorus and nitrogen > phosphorus > potassium respectively. The results of the frequency analysis show that for the target yield between 4200 and 4800 kg/ha and confidence interval 95%, the optimal fertilizer application rates of N, P2O5 and K2O, are 83.72–119.41, 64.10–134.39 and 78.80–147.20 kg/ha respectively, and for the total platycodin content over 5.5%, the optimal fertilizer application rates are 113.37–140.12, 85.96–153.44 and 76.86–136.38 kg/ha, respectively. Consequently, the optimal fertilizer application rates for both high yield and high quality of Platycodon grandiflorum are 113.37–119.41, 85.96–134.39 and 78.80–136.38 kg/ha, respectively. The corresponding fertilizer ratio of N:P2O5:K2O is 1:0.72–1.18:0.66–1.20.