A smoke guiding device of an aircraft gun nacelle comprises a closed-type smoke guiding structure composed of a plurality of clapboards and a smoke guiding shell. The closed-type smoke guiding structure and the aircraft gun nacelle are combined into a combination. The combination is installed on the lower portion of the front side of an aircraft air inlet passage, and an aircraft gun muzzle brake is wrapped with the combination. The clapboards are arranged in the smoke guiding shell, lower gas discharging ports are formed in the front end of the smoke guiding shell and below the smoke guiding shell correspondingly, and therefore high-temperature high-pressure waste gas originally discharged from the two sides of gun muzzle brake and the front side of the gun muzzle brake is converted to be discharged from the lower gas discharging ports in the front end of the smoke guiding shell and below the smoke guiding shell; and meanwhile, through the blocking effect of the clapboards, when the waste gas is discharged from the lower gas discharging ports of the smoke guiding shell, the waste gas quantity absorbed into the aircraft air inlet passage during aircraft gun shooting is reduced, and the problem that engine surge occurs due to the fact that the waste gas generated during aircraft gun shooting enters the aircraft air inlet passage is effectively solved, and the smoke guiding device of the aircraft gun nacelle has the characteristics of being simple in structure, low in weight and easy to install and maintain.