Protein requirements are different at different growth stage. Generally,crayfish in the early stage of life usually have a high protein requirements. An 8-week experiment was performed to investigate the effects of different dietary protein levels on growth performance,body composition and antioxidant capacity of Procambarus clarkii at three different growth stages. The results showed that with the increase of dietary protein level,WGR and SGR of crayfish increased first and then stabilized in three different growth stages. With the increase of dietary protein level,the FCR decreased first and then stabilized. In the first and second growth stage,the crude protein increased first and then stabilized; in the third growth stage,the lowest crude protein content was observed in the group fed with 250 g/kg dietary protein. With the increase of dietary protein level,both the superoxidase dismutase (SOD) activity and the phenoloxidase (PO) activity increased in the first and second growth stage; in the third growth stage,after the dietary protein levels exceeded 300 g/kg,both the SOD activity and the PO activity decreased. Based on these findings and a broken-line model of specific growth rate,the optimal diet protein levels for the crayfish with initial body weight of 0.026±0.001 g,1.04±0.03 g and 5.06±0.17 g,were 403.3 g/kg,358.8 g/kg and 305.6 g/kg,respectively.