A method of moment (MoM)-based current reconstruction method is proposed to estimate the surface current density on the ground plane. Current continuity property is automatically enforced with Rao-Wilton-Glisson basis function. Both the least square method and the optimization method are utilized to solve the inverse problem and obtain the ground current. The proposed optimization method is successfully validated with numeric simulations and also a real-world measurement example. The reconstructed current distribution on the ground plane is further used in a typical radio frequency interference (RFI) example to perform RFI estimation and provide guidelines for RFI design. The proposed MoM-based ground current reconstruction method can be valuable to estimate and debug RFI issues in early design stage.