Multistage multipoint water inlet enhanced denitrification sewage treatment system and method

The invention relates to a multistage multipoint water inlet enhanced denitrification sewage treatment system which comprises an AAO biochemical treatment module and an AO biochemical treatment module. The AAO biochemical treatment module comprises an anaerobic tank, a first anoxic tank and a first aerobic tank; the AO biochemical treatment module comprises a second anoxic tank and a second aerobic tank. Raw water is divided into at least two streams, one stream enters the anaerobic tank after being pretreated, effluent of the anaerobic tank enters the first anoxic tank, and effluent of the first anoxic tank enters the first aerobic tank; the other stream in the raw water enters the second anoxic tank together with the effluent of the first aerobic tank after being pretreated, and the effluent enters the second aerobic tank. The first aerobic tank is also provided with a nitrification liquid return pipeline connected with the first anoxic tank, and the second aerobic tank is also provided with a nitrification