The invention relates to a catalyst unified plasma nitric oxide removing device and method. Smoke and ammonia are mixed and then introduced to a gas inlet in the lower part of a reactor which is a dual-layer medium structure, a metal net layer wraps the outer side of an outer medium pipe as an external electrode, a metal internal electrode is arranged in an inner medium pipe and is connected with a power source anode, and the external electrode is connected with a power source cathode to form a plasma generator; in the middle of the reactor, a partition plate with air vents is arranged in a cavity between the outer medium pipe and the inner medium pipe and is added with a catalyst Fe-Cu/CNTs; the mixed gas is subjected to unified denitration by the combined action of the catalyst and the plasma, is introduced into an alkali solution cleaning device from a gas outlet in the upper part of the reactor, and is exhausted by a chimney after being cleaned and absorbed. Ethylene is mixed in the mixed gas to further improve a nitric oxide removing rate. The device can efficiently denitrify at high and low temperatures, has an NO removing rate more than 96%, small energy consumption and high economic benefits.