We have developed the high-frequency pulsed power generation system using ten or twenty MOSFETs in series. The operation principle of the circuit has been clarified, and the experimental results have confirmed the operation of the developed circuit. In the case of twenty MOSFETs the repetitive operation is verified at the output voltage of 10 kV and the frequency of 1 kHz. The pulse width of the output voltage was verified from 1 ƒÊs to 20 ƒÊs. The preliminary experiment of the underwater pulsed electrical discharge is performed, and the occurrence of the underwater pulsed electric discharge was confirmed.