The present invention discloses a light-operated adjustable terahertz wave attenuator. The attenuator includes a silicon base-silicon base-vanadium oxide thin film, a laser emitter and a spherical collimating lens, wherein the silicon based-vanadium dioxide thin film is vertical to a terahertz beam direction, the laser emitter is arranged on one side of the silicon based-vanadium dioxide thin film, the laser emitter is connected with the collimator, the laser emitted from the laser emitter is emitted from the collimator and irradiates on a film surface of the silicon based-vanadium oxide thin film, and the spots of the laser irradiating on the film surface of the silicon based-vanadium oxide thin film completely cover the transmitted terahertz wave spots. The present invention further discloses a use method of the light-operated adjustable terahertz wave attenuator.