Objective: To study the effects of the applied amounts and their ratios of nitrogen (N), phosphorus (P), and potassium (K) on the yield and active ingredients of Angelica dahurica var. formosana from Sichuan Province. Methods: The field tests on N, P, and K ratios of A. dahurica var. formosana from Sichuan Province were carried out by using orthogonal combination design, the yield was weighted, and the imperatorin and isoimperatorin contents in its roots were determined by HPLC method. Results: The yield and the quality of A. dahurica var. formosana from Sichuan Province were extremely affected by different N, P, and K ratios. The yield was increased with N, P, and K, but for imperatorin and isoimperatorin content, the influence of different N, P, and K ratios is very different. The imperatorin content was increased with the moderate increase of N and P under the lower level of K (K2O 120 kg/hm2). The isoimperatorin content was increased with the moderate supplies of N and P ratios under the high level of K (K2O 240 kg/hm2). Whatever the ratios of P and K, the imperatorin content and isoimperatorin content are lower than that in the control treatment under the high level of N (195 kg/hm2). The orthogonal analysis of variance results also showed that the effects of N, P, and K on the yield reached extremely significant. The sequence of them was P > N > K.. The influence of N, P, and K on imperatorin all reached extremely significantly different level (P < 0.01). Among them, the effect of P and K was higher than that of N. But only N had significant influence on the contents of isoimperatorin (P < 0.05). The adapted combined application program was N 150 kg/hm2, P 2O5 225 kg/hm2, and K2O 120 kg/hm2, namely the ratio of N- P2O- K2O was 1.3:1.9:1, by which the highest yield and imperatorin content were obtained. There were significant difference compared with the control and its isoimperatorin content was the highest as well. Conclusion: The above ratios of N, P, and K could improve the yield and quality of A. dahurica var. formosana from Sichuan Province as well as the content of imperatorin and isoimperatorin.