To compare the effects of supplemental yeast hydrolysates and small peptides in the feed of juvenile largemouth bass (Micropterus salmoides), the fish were fed with basal diet, diet supplemented with 1% yeast hydrolysates(YH) or 1% small peptides(SP) respectively to conduct 56-day feeding trial. Then the growth performance, liver-intestine health and anti-infection ability were investigated. The results showed that 1% yeast hydrolysates and small peptides had no significant effect on growth performance of juvenile largemouth bass. However the YH significantly reduced the amylase activity of mid- and hindgut, and increased the lipase activity of fore- and hindgut, while the SP significantly reduced the amylase activity of fore- and hindgut, and increased the lipase and protease activity of fore-, mid- and hindgut. In the SP group, the intestinal structure was smoother and clearer, and the cells on the surface of brush border were closely arranged, then the cup-shaped cells were more clearly visible. As for the serum biochemical indexes, the albumin content in YH and SP groups was significantly lower than the control group, and the alanine aminotransferase content was significantly higher than the control group. Also the lowest cholesterol and triglyceride content was observed in SP group. There was the strongest total antioxidant capacity and catalase activity of the liver in YH group. The strongest lysozyme activity of the head kidney and the lowest cumulative mortality rate after infection with Aeromonas hydrophila were shown in SP group. In summary, the addition of both 1% SP and 1% YH could improve liver and intestinal health and anti-infection ability, but each had its own advantages. SP had significant advantages in promoting the intestinal health and the immune protection of largemouth bass. While YH was more prominent in enhancing the antioxidant capacity of the liver. Consequently, it would be more beneficial to the overall health of juvenile largemouth bass when YH and SP were added in the feed selectively.