Abstract: Based on aerosol infrared radiation(IR) stealth technique,the characteristics of IR suppressant(3～5μm) on hot exhausts with spherical particles has been numerically investigated.The extinction characteristic parameters including extinction efficiency factor and asymmetry factor were calculated based on Mie scattering theory,which is decided by diameter parameter and complex index of refraction.The flow field was achieved by Fluent software,and IR radiation intensity of the target was calculated by ray-tracing-method.The parameters investigated include diameter parameter,complex index of refraction,concentration of the particles,injection velocity of the particles and coefficient of heat conduction of the particles.The results show that IR suppressant affected by the diameter parameter of discrete particles is the most prominent.And the best IR suppressant exists when the diameter of particles is in the range of 1.0μm.