Abstract: Under the condition of covering, a radon migration dynamics model of the uranium tailing pile was developed according to the characteristics of radioactive pollutants. In the process of the optimization of cover material selection, the multi-objective decision model was established which considered the radon exhalation rate and cost as decision objective. The model effectively integrated advantages of immune genetic algorithm and TOPSIS to solve the multi-objective decision model. The optimal values of physical property parameters of cover materials are obtained when the radon exhalation rate is minimal, and the optimal cover material is got by this model. The results of parameter optimization show that the radon exhalation rate is proportional to the porosity and diffusion coefficient of cover materials and inversely proportional to the thickness of cover material. The results of multi-objective optimization confirm that using the feasible solution asphalt can obtain the best benefit of environment and economy.