Abstract: Setting of radiation-well drainage system is an effective way to reduce the saturation line of ash dams, and it has been applied in a number of projects with remarkable effectiveness. While the key impact of the drainage effect of radiation-well is the layout of radiation-tube, especially when setting radiation-well drainage system in completed projects, due to complex terrain below the surface ash dam, radiation-tube lengths and angles are subjected to the stratigraphy and terrain conditions at the bottom of ash dam. The traditional design methods cannot fully consider these factors and they result in unreasonable design of radiation-tube layout or non-ideal seepage drainage. The design method for 3D radiation-well drainage system for ash dams, which is based on 3D modeling method and Boolean operation, can effectively avoid the problems mentioned above, achieve precise design and construction guidance purpose. This 3D method can be integrated with the seepage simulation analysis. It is an advanced and effective method for the design and verification of radiation wells. According to a case of radiation-well drainage project of ash dams, the new 3D radiation-well design method is proposed. Through numerical simulation analysis, the rationality of the proposed method is verified, and its feasibility is demonstrated.