Abstract: A high power multi-pulse modulator was presented which could generate three pulses with adjustable interval on the field-emission diode. In the system, a pulse transformer was employed to upgrade the discharging voltage of three groups of capacitors and charge the Blumlein pulse forming line. When the main gap being closed at interval of a certain time, three pulses were obtained on the field-emission diode, the peak power of each pulse was over 20 GW, pulse duration about 80 ns, and pulse interval about 15 ms. The simulation results agreed well with the experimental results. The experimental results showed that the recovery time of the main gap was an important effect factor on the pulse interval of the modulator.