Abstract: Measuring the concentration of the fault gas radon is an effective method to explore fault location and fault activity. Based on Abdoh and Pilkington’s two-dimensional partial differential equation and corresponding boundary conditions of radon migration, we establish three physical models of the overburden: internal fracture, fracture-fault and heterogeneous overburden. Then we solve these models and simulate radon migration in the overburden using partial differential toolbox (pdetool) and non-linear solution function (pdenonlin) on the Matlab platform. Finally, we analyze the simulation results of the three models, which explain the phenomena that the radon abnormal points on overburden surface are out of sync with the fault location. It is also interpreted the effect of thickness of overburden on the shape of the radon concentration curve, and impactions of the soil structural properties on the radon anomaly intensities and shapes.