The present invention discloses a system for strengthening a post-denitrification denitrogenation process. The system comprises a landfill gas inlet pipe, a nitrification strengthening tank (IN tank), a deaerator, a denitrification strengthening tank (ID tank) and a sedimentation tank, wherein the IN tank adopts landfill gas to aerate, the ID tank adopts the landfill gas with the oxygen removed by the deaerator to aerate, the length of the IN tank aeration pipe extending into the IN tank is 2 / 3 of the length of the tank, the IN tank and the ID tank are separated by a separation wall, the distance between the separation wall and the tank bottom is 1 / 5 of the height of the tank, the mixed ratio of the landfill gas to the air in the IN tank is 2:1-4:1, the internally circulated gas ratio in the IN tank is 50-80%, the internally circulated gas ratio in the ID tank is 70-90%, and the pre-acclimatization times of the microorganisms in the IN tank and the ID tank are 3-5 d. The system of the present invention has characteristics of high denitrogenation efficiency, stable treatment effect, simple process, less treatment structure and equipment, low infrastructure construction and operation cost, and the like.