Abstract: The effects of Yiduozyme P-8901 on the growth of tilapia(Oreochomis nilotica) were studied.Yiduozyme P-8901 was added to the base feed(control) at the rate of 100 g·t-1,150 g·t-1,and 180 g·t-1.There were 420 juvenile tilapia with an average individual body weight of about 5.1 g were randomly divided into 4 groups.Each group comprised 3 repetitions,and 35 fish per repetition.360 adult tilapia averaging 43.1 g each were also randomly divided into 4 groups.Each adult group consisted of 3 repetitions,and 30 fish per repetition.The results showed that in the juvenile groups,the feed efficiencies of the feed containing 100 g t-1,150 g t-1,and 180 g t-1 Yiduozyme P-8901 significantly increased by 8.48%,7.89%,and 9.03%,respectively(P0.05),as compared to the control.The body weight gain rates were significantly higher than the control group by 9.00%,10.33%,and 9.50%,respectively(P0.01);the growth rates significantly increased by 4.28%,5.41%,and 6.56%,respectively(P0.01);and,the protein efficiencies significantly increased by 8.38%,7.75%,and 8.84%,respectively(P0.01).For the adult fish,the feed efficiencies of the feed containing 100 g·t-1,150 g·t-1,and 180 g·t-1 Yiduozyme P-8901,significantly increased by 8.48%,7.89%,and 9.03%,respectively as compared to the control(P0.01);the body weight gain rates significantly increased(P0.05) by 6.31%,7.94%,and 8.82%,respectively;the growth rates significantly increased by 3.68%,4.72%,and 5.26%,respectively(P0.01);and,the protein efficiencies significantly increased by 5.36%,7.53%,and 9.24%,respectively(P0.01).The results suggest that adding enzyme P-8901 to the base feed could significantly improve feed utilization and growth performance.And,the effects were greater on the juvenile than the adult tilapia.