Abstract: The plasma-assisted slow-wave oscillator is a class of unique high-power microwave source, A class of fibre-optic controlled gases-puff system for plasma-cathode electron gun of the plasma assisted slow-wave oscillator is developed in this paper. Gases were injected into the hollow cathode, and the modulator is triggered at arbitrary delay to generate low-pressure glow discharge at the same time. And the discharge experiment of the electron gun in this system was presented. Operating on pulse-gas-puff-pressure at 0.28~0.4 Pa, representative discharge current up to 120~167 A, and transporting e-beam current up to 80 A.