Based on the discrete phase model in the simulation software FLUENT， the smoke diffusion characteristics under high-speed jet action of a smoke generator powered by a turbojet engine are calculated. Spatial distribution of smoke mass concentration in high-speed engine exhaust flow field is studied. The effects of smoke flow rate， engine exhaust flow rate and wind speed on the distribution of smoke concentration are also studied. The results indicate that within the range of action of the engine exhaust flow， smoke spreads in a conical shape， and in the downstream， smoke easily spreads upward due to the reverse flow effect. Environmental winds below grade three can suppress the upward diffusion of smoke and cover the ground with smoke at a greater distance. The increase of smoke flow rate and engine exhaust flow rate both can increase the smoke concentration and provide a larger effective protection range. The research can provide reference for the design of smoke generators powered by turbojet.