This study presents the numerical simulation of deep transcranial magnetic stimulation dTMS by considering the semi-Halo coil working with a circular coil, i.e., semi-Halo-circular assembly coil (sHCA coil). Three-dimensional distributions of the induced magnetic field and electric field in realistic head model were obtained by impedance method, and the results were compared with the normal Halo-circular assembly coil (HCA coil). It was found the potential disadvantage of wide distribution of the electric field under the perimeter of the HCA coil can be alleviated by employing the new coil design. The sHCA coil may offer a new tool for dTMS with potential for both research and clinical applications for psychiatric and neurological disorders associated with dysfunctions of deep brain regions.