Abstract：One problem of improved carrousel oxidation ditch of a sewage plant is the lower total nitrogen removal rate. Two solutions are put forward after analyzing the factors such as dissolved oxygen, C/N, sludge retention time, sludge return ratio and temperature. The results showed that power output of aerator is adjusted in accordance with the change of dissolved oxygen concentration monitoring in the corresponding site, which can also reduce energy consumption of the system. C/N of the anoxic zone is increased by adding one site of influent in anoxic zone. After reconstruction, the COD, BOD5 and NH4+?N of effluent are stable, and the total nitrogen removal rate is significantly increased from 56.25% to 68.80%.