The invention discloses a multiphase synergistic nitrogen based sewage treatment device. The device comprises a dilution tank, a pre-acidification tank and an anaerobic tank, wherein the bottom of thedilution tank is communicated with a water inlet of a first water pump arranged on the side of the pre-acidification tank through a pipeline, and a water outlet of the first water pump is communicated with the top of the pre-acidification tank; the bottom of the pre-acidification tank is communicated with a water inlet of a second water pump fixedly connected to the side of the anaerobic tank through a pipeline, and a water outlet of the second water pump is communicated with the top of the anaerobic tank; a transparent window is formed in the front of the dilution tank, and volume scale lines are arranged on the transparent window; a first liquid inlet and a second liquid inlet are formed in the top of the dilution tank respectively. By means of the design of the pre-acidification tank,sewage can be effectively mixed with multiphase synergistic nitrogen when multiphase synergistic nitrogen is added to the anaerobic tank, the effect of multiphase synergistic nitrogen in the anaerobictank is effectively developed, and the sewage treatment rate is increased; the device is high in practicality and easy to popularize and use.