The influence of density on the welfare of juvenile jade perch during the 50–100 g growth stage was investigated in this paper. The experiment was conducted in tanks equipped with a biological filter, and two tanks for each density were used. The three densities studied were low density (LD, 100 fish /m³ , 5 kg/m³ ), medium density (MD, 260 fish/m³ , 13 kg/m³ ), and high density (HD, 360 fish/m³ , 18k g/m³ ).The experiment lasted 45 d. The welfare of the fish was studied by recording growth and physiological parameters during the whole period. Within the size and density range tested, fish welfare was impacted negatively by increasing density. The serum cortisol, alanine aminotransferase (ALT) activity, and aspartate aminotransferase (AST) activity levels differed significantly (P < 0.05) among the three densities in 15 d, but at the end of the experiment（45 d） the significance disappeared. The effect of density on the serum C3 level was delayed, and a significant difference was not detected until the experiment ended. The body weight showed a significant difference among the three densities. The average body weight of the LD group was 96.62 ± 2.99 g, and that of the HD group was （75.54±6.36） g. The results showed that although the perch in this study were able to withstand the negative effects of high stocking density, it still influenced the fish’s growth.