Three membrane bioreactors (MBRs) were operated to investigated the effect of continuous chemical cleaning on membrane fouling for wastewater treatment at NaOH concentration 0 (control), 0.004, 0.04 N, respectively. The results showed that the cake resistance decreased with the increase of NaOH concentration. However, the fouling resistance was reduced effectively at NaOH concentration of 0.004 N, and this effect weakened significantly at a higher concentration of 0.04 N. Detailed studies on the effect of chemical cleaning indicated that a NaOH concentration of 0.004 N was the optimum in terms of nutrients removal and permeate flux.