The effect of N, P and K fertilizer on alfalfa yield and suitable fertilizer rate were studied in field using ‘3414’ experimental design in Changchun. The results showed that compared with CK, the yield of alfalfa in-creased by 1.09% to 24.21% with application of N fertilizer, increased by 57.39% to 135.86% with application of Pfertilizer, and increased by 20.44% to 62.61% with application of K fertilizer. The relative yields of alfalfa under Pfertilizer deficiency treatment, K fertilizer deficiency treatment and N fertilizer deficiency treatment was 37.53%,54.69% and 71.58%, respectively. The abundance and deficiency condition of available P, K and N fertilizer treat-ment were serious deficiency, medium and great abundance, respectively. By the method of fertilizer effect functionindex, the proper amount of N for alfalfa was 9.32 kg/hm², the proper amount of P₂O₅ was 103.92 kg/hm², and theproper amount of K₂O was 34.56 kg/hm².