This invention provides a metering and discharge device for measuring residual liquid in analgesic pumps, addressing the field of volume measurement for residual liquid in such devices. Analgesic pumps typically administer neuromedicinal drugs, and hospitals maintain strict control over dosage administration. The technical solution comprises a storage tank equipped with a liquid level sensor, a laser emitter mounted on the tank’s top or upper surface, and a photosensitive plate positioned at the tank’s bottom to detect laser signals. The laser emitter, liquid level sensor, and photosensitive plate are interconnected via electrical or signal links. The storage tank is connected to a liquid discharge system for removing residual medication. This innovation enables precise measurement of post-administration liquid volume in analgesic pumps and automatically discharges it into drainage systems through standardized metering mechanisms. This implementation facilitates closed-loop management of drug consumption, enhances precision and intelligence in controlled substance administration, significantly improves measurement accuracy and efficiency, and supports hospitals in achieving comprehensive closed-loop management of analgesic pump medications.