The invention proposes a Hall thruster plume circumferential instability monitoring device, relating to the Hall thruster monitoring technology field and aiming to meet the monitoring requirement of plume circumferential instability. According to the invention, both the reflective objective lens and reflective eyepiece are located inside the vacuum chamber and outside the Hall thruster plume area, and the light at the exit of the discharge channel of the Hall thruster is incident on the ICCD camera via the reflective objective lens, the reflective eyepiece and an interference filtering sheet successively wherein the ICCD camera is connected to the computer. The device of the invention is suitable for monitoring the Hall thruster plume circumferential instability.