Abstract: The present paper aims to introduce research of the effect of organic carbon on the denitrogenation using simultaneous nitrification and denitrification in moving-bed biofilm reactor.COD/TN ratio was about 3 in real domestic wastewater. The result of the treatment show that at the end of aeration the average removing rate of TN,NH₄⁺-N and COD can reach 59.8%,83.12% and 94.9%,respectively.In order to improve the efficiency of removing TN,the experiment added amylum,glucose and methanol.The results show that adding organic carbon can improve the degradation of COD and nitrogen.When adding amylum,COD degradation was incomplete and leaded to the system performance deterioration.When adding methanol and glucose,the TN removal ratio reached 84.5% and 80.55%,respectively.But considering factors of security and economy,adding glucose is more appropriate.