Abstract: In order to explore the effect of cellulase on the quality and nutritional composition of Stylosanthes guianensis silage, Stylosanthes guianensis cv. Reyan No.2 was divided into control（CK group） group and 4 cellulase addition groups（S1-S4 groups） with 3 repeats in each group. The control group did not add cellulase, and the S1-S4 groups was supplemented with 5, 10, 20 and 40 mg/kg cellulase. After 30 days of silage, the silage quality and nutritional composition were analyzed. The results showed that the dry matter content and crude protein content in S1-S4 groups were significantly higher than those of CK group（P＜0.05）, while the contents of neutral detergent fiber and acid detergent fiber were significantly lower than those in the CK group（P＜0.05）. The pH value of Stylosanthes guianensis silage in the S1-S4 groups were significantly lower than that in CK group（P＜0.05）, and the lactic acid content in the S1-S4 groups were significantly higher than that in the CK（P＜0.05）. Compared with the control group, the dry matter, crude protein and lactic acid content in the S4 group（adding 40 mg/kg cellulase） increased by 10%, 12%, and 69%, respectively, and the content of neutral detergent fiber, acid detergent fiber and pH decreased by 10%, 8% and 15%, respectively. The results indicated that the addition of cellulase to Stylosanthes guianensis could effectively improve the quality and nutritional value of silage, and the addition of 40 mg/kg cellulase was more suitable.