This paper numerically confirms that in the ideal case, the form of cone with 16 ribs benefits the reduction in impedance and the promotion (about 20%-30%) on transmission efficiency of a magnetically insulated transmission line, in comparison with the traditional form of cone. Magnetically insulated transmission lines in the form of cone, cone with 4, 8, 12, and 16 ribs, are first designed by using CREO and then imported to COMSOL for obtainment of their circuit parameters. Two codes based on the wave process and wave process coupled with RLC circuits, respectively, simulating the propagation of external waves through non-uniform transmission lines are analyzed and presented in detail. The obtained parameters are then used in these codes for deriving the designed transmission lines' transmission efficiency of peak power. As a comparison, the obtained data are also employed in PSpice for derivation of the transmission efficiency. These derived results consistently verify that the form cone with ribs may effectively promote the transmission efficiency of magnetically insulated transmission lines.