The scheme of a dual short pulse output structure is proposed, according to the concept that two microwave device driven by the same pulsed accelerator can produced stable dual-frequency high power microwave (HPM) simultaneously. Structure model of a dual short pulse output structure is designed, which is connected to the main switch and can transmit the high voltage nanosecond pulse generated by the switch to the HPM generator. The two-channel pulse is produced by the same pulse source and has good consistency. In this paper, the pulse transmission process of the dual short pulse transmission structure is modeled and simulated, and the influence of electrical parameters such as transmission line impedance and input pulse front on output waveform quality is studied. The risk analysis about insulation and structural optimization are completed. It is estimated that the output pulse quality of the simultaneous output line is equal to that of the single transmission line under 4-8 ns quasi-square wave input pulse, and the overshoot oscillation is less than 20%, the flat top oscillation is less than 1%, and it can meet the insulation requirement.