On the basis of the theory of diffusion and convection of radon, the predent paper has formulated migration equations in arbitary media as well as in rock and soil near the surface, and set up a model for ground atmosphere exchange of radon.The migration regularity of radon in media has been studied and the theoretical equations verifield by model experimentation. The authors used the theoretical model to calculate the radon concentration of air at a certain residential area of Linchuan City, Jianxi Province, which has been preliminarily proved to the effective.