A plasma denitrification device, characterized in that it comprises: a plasma generating device, which comprises a plasma generator and a pulsed power supply; the plasma generator comprises at least one set of an electrode configured to generate plasma; an inlet of the plasma generator is configured to allow sewage passage; a denitrification reservoir, which comprises a shell and a denitrification zone, a water purification zone, and a sludge collecting zone provided inside the shell; the denitrification zone and the water purification zone are adjacently arranged, the sludge collecting zone is arranged below the denitrification zone; a water inlet is provided at a side wall of the denitrification zone, a water outlet is provided at a side wall of the water purification zone; a partition is provided between the denitrification zone and the water purification zone, and a water passage is provided at the partition; the denitrification zone and the water purification zone are connected through the water passage; a bottom of the denitrification zone is provided with a sludge collecting opening, the denitrification zone and the sludge collecting zone are connected through the sludge collecting opening; a sludge discharge opening is provided at a bottom of the sludge collecting zone; the denitrification zone is provided with a water distributor, the water distributor evenly distributes sewage into the denitrification zone; an inlet of the water distributor connects an outlet of the plasma generator through the water inlet; an outlet of the water distributor is provided at the bottom of the denitrification zone; the denitrification zone is provided with a catalyst layer, the catalyst layer comprises one or more selected from the group consisting of palladium, nickel, rhodium, copper, and iron; or comprises one or more selected from the group consisting of an oxide of palladium, an oxide of nickel, an oxide of rhodium, an oxide of copper, and an oxide of iron; the plasma generator has a pulse voltage of 0.3 kV-30 kV, a current density of 1 - 10 mA/cm 2, an operation frequency of 5-80 kHz; the partition comprises an upper slotted partition and a lower slotted partition arranged adjacent to each other, the upper slotted partition borders the denitrification zone, the lower slotted partition borders the water purification zone; the water passage comprises an upper water passage and a lower water passage, the upper water passage is provided at a top of the upper slotted partition, the lower water passage is provided at a bottom of the lower slotted partition; a space between the upper slotted partition and the lower slotted partition constitutes a water passage route. an upper surface of the catalyst layer is lower than a bottom of the upper water passage, a lower surface of the catalyst layer is higher than an outlet of the water distributor. a plasma generating device, which comprises a plasma generator and a pulsed power supply; the plasma generator comprises at least one set of an electrode configured to generate plasma; an inlet of the plasma generator is configured to allow sewage passage; a denitrification reservoir, which comprises a shell and a denitrification zone, a water purification zone, and a sludge collecting zone provided inside the shell; the denitrification zone and the water purification zone are adjacently arranged, the sludge collecting zone is arranged below the denitrification zone; a water inlet is provided at a side wall of the denitrification zone, a water outlet is provided at a side wall of the water purification zone; a partition is provided between the denitrification zone and the water purification zone, and a water passage is provided at the partition; the denitrification zone and the water purification zone are connected through the water passage; a bottom of the denitrification zone is provided with a sludge collecting opening, the denitrification zone and the sludge collecting zone are connected through the sludge collecting opening; a sludge discharge opening is provided at a bottom of the sludge collecting zone; the denitrification zone is provided with a water distributor, the water distributor evenly distributes sewage into the denitrification zone; an inlet of the water distributor connects an outlet of the plasma generator through the water inlet; an outlet of the water distributor is provided at the bottom of the denitrification zone; the denitrification zone is provided with a catalyst layer, the catalyst layer comprises one or more selected from the group consisting of palladium, nickel, rhodium, copper, and iron; or comprises one or more selected from the group consisting of an oxide of palladium, an oxide of nickel, an oxide of rhodium, an oxide of copper, and an oxide of iron; the plasma generator has a pulse voltage of 0.3 kV-30 kV, a current density of 1 - 10 mA/cm 2, an operation frequency of 5-80 kHz; the partition comprises an upper slotted partition and a lower slotted partition arranged adjacent to each other, the upper slotted partition borders the denitrification zone, the lower slotted partition borders the water purification zone; the water passage comprises an upper water passage and a lower water passage, the upper water passage is provided at a top of the upper slotted partition, the lower water passage is provided at a bottom of the lower slotted partition; a space between the upper slotted partition and the lower slotted partition constitutes a water passage route. an upper surface of the catalyst layer is lower than a bottom of the upper water passage, a lower surface of the catalyst layer is higher than an outlet of the water distributor.