Abstract: High-frequency fast-front nanosecond pulse is widely used in grid equipment detection, plasma jet, material optimization and modification. Diode opening switch (DOS) based on LC resonant boost and reverse fast truncation can generate ultra-short nanosecond pulses in different application scenarios. The oscillation duration of the resonant network causes the theoretical extreme value of the maximum operating frequency. Meanwhile, the significantly increased resistance losses under high-frequency output seriously impair the safe operation of the power supply. In this paper, the topology of high-frequency ultra-short nanosecond DOS power supply with modular frequency superposition is studied. The DOS circuit model considering diode parasitic parameters is established, and the parameter configuration of high-voltage gain resonant network is defined to reduce the switch on/off voltage and current stress. The modular magnetic isolation cascade circuit is designed to find out the optimal interval of the isolation inductance parameters and realize higher amplitude operation of the module. A multi-level modular frequency superposition control strategy is proposed to improve the energy conversion efficiency and break through the high-frequency operation extrema of DOS circuits. The experimental results show that the output pulse amplitude is 1 860 V(variable ratio gain 10.3), and the FWHM is 7.0 ns. Under the modular operation, the energy conversion efficiency is increased by 320 %, and the pulse waveform repetition frequency at the load end is 10 MHz. The experimental results are consistent with the theoretical analysis.