In order to explore effects of dietary Haematococcus pluvialis on growth, antioxidant enzyme activity, immune response and ammonia tolerance in yellow catfish. Yellow catfish (5.00±0.85) g was selected as the study object. The four diets were formulated to contain four graded dietary H. pluvialis levels: 0.00% (control), 0.30%, 0.50% and 1.00%. Each diet was randomly assigned to triplicate groups of 30 fish twice daily to apparent satiation. The experiment lasted for 10weeks. The results indicated that fish fed the diet containing H. pluvialis more than 0.30% showed the highest weight gain rate and hemoglobin content, and the lowest feed conversion ratio and white blood cell count. Serum superoxide dismutase and glutathione peroxidase activities and malondialdehyde content of fish fed 0.50% H. pluvialis diet were lower than those of fish fed other diets, but serum lysozyme activity was higher. Cumulative mortality and blood ammonia level in fish fed 0.50%~1.00% H. pluvialis were lower than those of fish in control group after being exposed to ammonia for 96 hours. Dietary supplementation of H. pluvialis significantly increased the contents of ammonia metabolism enzymes in liver of fish exposed to ammonia, and the contents of carbamyl phosphate synthase and argininase were significantly increased with the increase of the H. pluvialis levels. The results showed that dietary supplementation of more than 0.30% H. pluvialis could significantly improve the growth, blood health status, oxidative damage and immune response of yellow catfish. The survival rate of yellow catfish exposed to ammonia can be significantly improved by adding more than 0.50% of H. pluvialis in the diet.