This article describes an impulse voltage generating device combined of modular multi-level structure, which can replace the ignition gap in the traditional Marx circuit, avoiding the synchronization and interference problems. In this paper, the components, the specific structure, charging method, analysis of its working principle and modulation theory of this device are introduced concretely. And in the MATLAB / SIMULINK, Marx equivalent circuit and equivalent formula are built to generate the traditional lightning impulse voltage. Then, a 100-level impulse voltage generation structure based on modularized multi-level with the carrier modulation is also built, the voltage waveforms of Marx equivalent circuit and equivalent formula are respectively used as the modulation waveforms for tracking and comparison. After obtain the related voltage waveform results and front time and half-peak time parameters, it is proved that this structure can produce a qualified surge voltage.