Most high temperature superconducting (HTS) devices have been established by employing a single tape or a few tapes in parallel. These HTS devices generally have large current carrying capacity at present. Therefore, a cable with high current density becomes a key point for the application of HTS devices. In previous works, a core cable has been described and the thermal stability of the superconducting winding using the core cable is analyzed. In this paper, first the core cable is introduced which has a copper former and two conductor layers, internal layer and external layer. Subsequently, a finite-element analysis model of the core cable is built to analyze the electromagnetic characteristics of each conductor layer by taking seven design parameters into consideration: Cable A, Cable B, Cable C, Cable D, Cable E, Cable F, and Cable G with different pitch angle and twist pitch, and the structure parameters of the core cable are optimally designed on the basis of the electromagnetic characteristics analysis. Finally, the short core cable sample consisting of YBCO coated conductor with an outer diameter of 6 mm, and the critical current of about 500 A @77 K, self-field, and experimental platform are all made to verify the core cable design and analyze the changes of current-carrying features of the core cable along with the extra magnetic field. According to the results, when the core cable is applied in HTS devices (such as HTS transformer), extra magnetic field intensity of the core cable is better to be less than 0.1 T.