[Abstract] Object: To investigate effects of rearing density on growth and development of the zebrafish. Materials and method: Zebrafish was maintained at 1, 2, 4, 6, 8 Tail/L density in a 3L indepent unit. In some distinct developmental stages, the weight, length, organ weight of fish was measured and some indicators were calculated. The results of weight, DWG, GBW, GBL and viscera index were analyzed by SPSS 17.0. Result: There was no significant difference among each group ,when the rearing density differ from 1 to 4 Tail / L. However, the weight, DWG, GBW, GBL and viscera index descend when density is increasing, and there was a significant difference between the groups of low density (P< 0.01). Conclusion: In a comprehensive consideration of considering the factors that affect the efficacy of breeding including space and the quality of living environment of zebrafish et al , 4 Tail / L is an ideal rearing density.