Abstract: In order to optimize the condition of continuous domestic wastewater treatment by Chlorella zofingiensis (C. zofingiensis) and to improve the treatment efficiency, the effects of different renewal rates on the treatment efficiency were studied. Six different renewal rates (0.20, 0.30, 0.40, 0.50, 0.60 and 0.70 d ^-1) were set for the experiment using C. zofingiensis to continuously treat domestic wastewater in the column photo bio-reactor. Through the experiments, the parabolic regression curve of the renewal rate, the cell yield, nitrogen and phosphorus consumption rate were established to find the optimal range of renewal rate. The results showed that the renewal rate had significant effects on the growth of C. zofingiensis and the treatment of pollutants. During the continuous reaction, with the increase of renewal rate, the algal cells concentration at steady state decreased gradually, while the effluent nutrients concentration increased. There is a parabolic regression relationship, between the renewal rate (x) and the cell yield (P) respectively, the nitrogen consumption rate (y₁), the phosphorus consumption rate (y₂) :P=-1.179(x-0.45) ²+0.026(x-0.45)+0.239(R ²=0.990 9), y₁=-66.79(x-0.45) ²+2.55(x-0.45)+10.26(R ²=0.936 7), y₂=-19(x-0.45) ²+1.963(x-0.45)+2.913(R ²=0.924 5). The determination coefficient R ² of three curves is high, and the extreme values are all 0.45 d ^-1 which can be considered as the optimal renewal rate.