Abstract: This experiment was conducted to investigate the effects of different levels of yeast hydrolysate (YHY) supplementation on growth performance, digestion, antioxidant and non-specific immunity of red swamp crayfish, Procambarus clarkii. A total of 300 crayfish with an average weight of (6.43±0.55) g were randomly divided into 5 groups (with 3 replicates in each group). These groups were fed with the basic diet supplemented with 0 (control group), 0.5%, 1%, 2% and 4% YHY, respectively. At the end of 8-week experiment, the growth performance, digestive enzyme activities of gastric tissue and hepatopancreas, antioxidant and immune capacities of hepatopancreas and serum biochemical indexes were determined. The results showed as follows: (1) YHY supplementation at levels ranging from 1% to 4% positively influenced the growth performance of P. clarkii. The 2% supplementation group exhibited peak values in survival rate (SR), final body weight (FBW), final body length (FBL) and hepatopancreatic index (HSI), being significantly higher than those in the control (P<0.05). The 1% supplementation group demonstrated the highest weight gain rate (WGR) and specific growth rate (SGR), which were significantly higher than those in other groups (P<0.05). (2) The crude protein (CP) content of whole body in 1.00% YHY supplementation group was significantly higher than that in any other group (P<0.05). The CP and crude lipid (CL) contents of muscle reached the maximum values in 2.00% supplementation group. (3) Gastric and hepatopancreatic digestive enzyme activities witnessed significant increases in groups supplemented with 2% to 4% YHY compared with the control (P<0.05). (4) The activities of antioxidant enzymes (catalase, CAT; total superoxide dismutase, T-SOD and total antioxidant capacity, T-AOC) and immune enzymes (alkaline phosphatase, AKP and acid phosphatase, ACP) in hepatopancreas reached their maximum values in the 2% YHY supplementation group, the malondialdehyde (MDA) content reached the minimum value concurrently, and there were significant differences compared with the control group (P<0.05). (5) Serum total protein (TP) and albumin (ALB) contents were notably higher in 2% YHY supplementation group compared to other groups (P<0.05). The activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were significantly lower in 1% and 2% supplementation groups relative to other groups (P<0.05). The results showed that 2% dietary yeast hydrolysate could significantly enhance the digestion, growth performance and muscle’s CP and CL contents, as well as significantly improve the antioxidant capacity and non-specific immunity of P. clarkii.