Abstract: The present invention discloses a plasma denitrification device, which comprises a plasma generating device and a denitrification reservoir. The plasma generating device comprises a plasma generator and a pulsed power supply. The plasma generator comprises at least one set of an electrode to generate plasma. An inlet of the plasma generator is configured to allow sewage passage. The denitrification reservoir comprises a shell and a denitrification zone, a water purification zone, and a sludge collecting zone provided inside the shell. The present invention effectively reduces total nitrogen and ammonia nitrogen in the polluted water body and helps to reduce COD, BOD, total phosphorus and chroma of the water body. The dissolved oxygen level of the water body is also increased after the purification process.