Vadose zone is the important media that contaminant enters into the groundwater, and it plays a crucial role in the strength of pollution sources. HYDRUS-1D model is used to simulate the transportation processes of contaminant in the vadose zone before entering into the groundwater, a process-based evaluation system for groundwater pollution is built. By taking a tail pond as an example, a coupling study on the transportation simulation and pollution evaluation of the contaminant in the soil-groundwater system is conducted. The result shows that the impact assessment based on the process is able to reflect the temporal and spatial variation of the groundwater pollution sources more accurately than traditional groundwater quality impact assessment does. The theory perfects the theory of prediction and evaluation of groundwater pollution, provides a theoretical basis and practical guidance for the prevention of groundwater pollution.