The invention relates to a system and method for enhanced nitrogen removal of sewage through denitrification. The system for enhanced nitrogen removal of sewage through denitrification comprises an anaerobic pool, an anoxic pool, an aerobic pool and a secondary sedimentation pool which are in successive connection. The system further comprises a control system, wherein the control system is connected with an aeration system and a carbon source feeding system; the control system controls the aeration of an aerator so as to allow the DO concentration of the aerobic pool to be 0.5 to 2.9 mg / L andthe ammonia nitrogen concentration of an effluent to be 0.5 to 1.5 mg / L; the carbon source feeding system comprises a nitrate nitrogen on-line monitor and a carbon source feeding device; the nitratenitrogen on-line monitor feeds a nitrate nitrogen concentration back to the control system; and when the nitrate nitrogen concentration of the effluent of the aerobic pool is higher than the set valueof 10 mg / L, the control system controls the carbon source feeding device to feed 5 to 7 units of a carbon source per unit of nitrate into the anoxic pool. According to the invention, intermittent aeration of a sewage treatment plant is realized, so the effluent stably reaches the standard, and energy consumption in aeration is saved; meanwhile, highly-efficient nitrogen removal is realized through accurate chemical feeding in an anoxic area by using the carbon source feeding system according to the nitrate nitrogen concentration of the effluent, so energy consumption in aeration can be saved,and the DO concentration of a reflux liquid is reduced; and the carbon source is accurately added according to the nitrate nitrogen concentration, so highly-efficient denitrification is realized, andthe cost of the carbon source is saved.