The invention discloses a high-voltage high-repetition-frequency pulse modulator 20KV unit module which comprises: a pulse leading and falling edge forming circuit for forming positive and negative pulse signals; a dual-stage transformer circuit for dual-stage single-column magnetic drive transmission; a gate driving waveform adjusting circuit for adjusting a gate driving waveform; and a switchingtube and voltage-equalizing network. The specific operating principle of the unit module is that when a leading and falling edge pulse signal passes through a high-voltage bus, the dual-stage transformer circuit transmits the leading and falling edge pulse signal to the gate driving waveform adjusting circuit to form a pulse so as to synchronously switch on/off the switching tube, and simultaneously the voltage-equalizing network protects the operation of the switching tube. The unit module separates an insulation function and a voltage transformation functions, and is realized by one main insulating transformer driving n driving transformers. The driving transformers have low voltage withstand requirements, small volumes and light weight. The main insulating transformer passes through the high-voltage bus, and is firm, reliable, and easy to disassemble. The unit module has low a corresponding dynamic voltage equalization processing difficulty, releases less EMI energy, and has good expansibility.