Based on modified HC, the influence of red phosphorus（RP）content on smoke spectrum transmissivity, initial concentration, settling velocity and particle size distribution is studied. Smoke chamber experiment results show that when RP content is 0% ,the average infrared spectrum transmissivity is 22.4% with smoke in 8~14 μm; when RP content is 10% ,the average infrared spectrum transmissivity is reduced to 7.8% in the same smoke region.