Abstract: An experiment was carried out to study the effect of different N, P, K fertilizer treatments on the yield and quality of Stylosanthes guianensis cv. Reyan No.2, according to the theory of “3414” regression optimum design, the result showed that: the yield of different treatments of formula fertilization is significantly higher than unfertilized application (CK), the highest fresh yield of 3 997.6 kg/667 m² is reached by the application of N 4.33 kg/667 m², P₂O₅ 3.93 kg/667 m² and K₂O 3.75 kg/667 m² (6th treatment). Under the three-factor model, the optimum fertilization amounts of S. guianensis. cv. Reyan No.2 are N 4.33 kg/667 m², P₂O₅ 3.93 kg/667 m² and K₂O 3.75 kg/667 m², the optimum fresh yield is 3 862.5 kg/667 m². There is a regular that in the vegetative stage, contents of crude protein (CP) and crude ash (Ash) are higher, contents of the crude fiber (CF), crude fat (EE) and nitrogen free extract (NFE) lower than in the early flower stage.