Abstract: This paper investigates the effects of the impedance, and transmission voltage and current of magnetically insulated transmission lines(MITLs) on the current of the generated space electron flow and the thickness of the cathode electron sheath. The three-dimensional approximate model of the four-layer disc cone MITLs is established and simulated by CHIPIC software. The comparison of the theoretical calculation, the three-dimensional simulation values and the two-dimensional simulation results of some relevant literatures verifies the correctness of the three-dimensional simulation. Finally, the effects of the distance changes between anode and cathode on transmission efficiency of the disc cone MITLs are studied.