In this paper, we studied effect of the breeding density and water quality on Epinephelus coioides in the growth, feed coefficient and immunity. Total 450 groupers whose average weight was 146.3 g/tail were divided into three experiment densities. The initial densities were 14.6, 21.7 and 29.5 kg/m³, respectively. The results showed that, the content of ammonia nitrogen was influenced significantly (P<0.05) by the stocking density, and the feeding rate of Epinephelus coioides showed a significant negative correlation with the ammonia N maintained time and concentration. Under the same experiment conditions, higher stocking densities have a negative effect on fish growth. The specific growth rate of the three treatments was 1.07, 0.60 and 0.47, respectively. With the augmentation of density, the weight of experiment groups showed a significant difference, in which the weight gain of each treatment was 118.5, 63.3 and 44.1 g, respectively. It was also found that the stocking density had insignificant impact on feed coefficient rate and survival rate. The immunity content of lysozyme (LZM), alkaline phosphatase (AKP) and superoxide dismutase (SOD) decreased with increased density, and showed a trend of increase at first and then decreased with the extension of culture period. The article revealed that one mechanisms of breeding density influenced Epinephelus coioides growth, maybe density caused water quality to change, which in turn affects the feeding rate of Epinephelus coioides, and resulting in the significant difference in growth performance of different density grouper.