The invention relates to a pulverized coal tank inert gas protective device and an application method thereof. The pulverized coal tank inert gas protective device comprises a CO2 output pipeline and an N2 output pipeline; a first general control valve, a first decompression table, a first vaporizer, a first inerting controller and a first throttling valve; one end of the CO2 output pipeline is connected with a CO2 storage device, while the other end of the CO2 output pipeline is connected with more than one CO2 branch pipeline; each CO2 branch pipeline is connected with the upper part of one powder tank; the N2 output pipeline is orderly connected with a second general control valve, a second decompression table, a second vaporizer, a second inerting controller and a second throttling valve in series; one end of the N2 output pipeline is connected with a N2 storage device, while the other end of the N2 output pipeline is connected with more than one N2 branch pipeline, and each N2 branch pipeline is connected with the lower part of one powder tank; a monitoring device is arranged on each powder tank; each monitoring device is connected with a control system; the control system is connected with a first general control valve and a second general control valve, respectively. The pulverized coal tank inert gas protective device is capable of not only effectively preventing spontaneous combustion of the pulverized coal, but also introducing the insert gas into the pulverized coal tank slowly, thereby enabling the pulverized coal particles to be stable slowly.