A municipal wastewater treatment plant in Zhaoqing city capable of treating 20000 m³·d^-1 wastewater was available in June 2008.With the success of cultivating activated sludge in July,the adjustment of treatment parameters was performed to improve the treatment efficiency in the following two months that ensured the effective operation of the plant in November.By using the standard monitoring methods,several kinds of contaminants and indexes,including chemical oxygen demand(COD_Cr), biochemical oxygen demand(BOD₅),ammonia-nitrogen(NH₄⁺-N) and total phosphorus(TP) were utilized to determine the treatment efficiency of the plant.The results showed that the influent consistency of COD_Cr,BOD₅,NH₄⁺-N and TP ranged from 117.3 to 446.4 mg·L^-1,60.5 to 225.9 mg·L^-1,7.6 to 34.3 mg·L^-1,and 1.85 to 5.49 mg·L^-1 respectively.After treated,the cyclic activated sludge system could dramatically decrease the concentration of those contaminants to 18.6 to 63.2 mg·L^-1, 8.0 to 29.2 mg·L^-1,2.0 to 8.8 mg·L^-1,and 0.22 to 0.83 mg·L^-1.Effluent could return back into the environment with the match of discharge standard of pollutants for municipal wastewater treatment plant and local criteria.The total amounts of bacteria,yeast and mould were 4.2×10¹⁰±1.8×10¹⁰ CFU,2.5×10⁷±1.8×10⁷ CFU,and 3.6×10⁶±2.6×10⁶ CFU per gram dry sludge respectively in the operation period.