The present paper begins with a brief description of tens of newest tech niques for determining radon and its daughter products. Then. regarding the migration mechanism of radon, the authors advance a "composite model of geo-chemical halos" which emphasizes the view that radon, travels integratedly and by stages. They also give an account of some recent interpretations on radon migration put forward by researchers in the world, which include such theories as diffusion, convection, drawing and transportation. With some practical appli cations as examples, they point out the effectiveness of applying radon survey to prospecting, especially to prospecting for radioactive ore resources.