Abstract: The dynamics of smoke particles can be effectively described by the Stokes sedimentation theory and diffusion coefficient expression in normal conditions; but in vacuum and microgravity, the forementioned principles are not applied any longer. In order to study the applicability of the IR smoke in outer space, by analyzing the vacuum and microgravity effects of the smoke particles, we can simulate approximately the dynamics property of smoke particles using molecule dynamics theory. On the basis of correlative theory, the force between particles is related to the space between them. When the space is less than ten times balance space, the force is large enough to form steady smoke, otherwise, the force is too small, smoke particles cannot form steady smoke. According to the Maxwellian distribution function, a function model of space between particles is established. Based on the model, the effects of smoke materials radius r, consistency ρ and the moving time of particles t on the space between smoke particles are discussed by Mathematica method. The results show that the space reduces with the increasing of the r and ρ, the smoke screen stability will increase gradually; the more long t is, the more the space is large, the smoke screen stability will decrease.