Abstract: High voltage pulsed power technology has a wide range of applications in the fields of national defense, insulation materials, biomedical engineering, etc. In order to study the bioelectric effect of hundreds-nanosecond pulse electric fields on cells, an all-solid-state Marx hundreds-nanosecond generator based on 'back-to-back' charging and hybrid isolation has been designed. The device has 5 stages, with MOSFET as the main discharge switch, contains 9 capacitors and 5 switches, thus the switch usage is reduced. The module at each level contains 2 capacitors and 1 MOSFET switch, and 2 capacitors are charged separately by the positive polarity loop isolated by the resistance and the negative polarity loop isolated by the diode to achieve 'back-to-back' connection. The Pspice software is used to verify the feasibility of the topology. The hundreds-nanosecond pulse device uses a field programmable gate array (FPGA) to generate control signals, and the output high-voltage pulse parameters are as follows: the voltage amplitude is 0~4.3 kV, the pulse width is 0.3~5 µs, the repetition frequency is 0.001~10 kHz, and the rising edge is 42 ns. The pulse width, amplitude and frequency of the device are all flexibly adjustable. Through the modular design, the number of modules can be increased to further improve the output voltage amplitude.