This paper introduces a monitoring system of musle relaxant in action during the operation under general anaesthesia. The design of the monitor is based on measurement of acceleration. It consists of an acceleration transducer, a nerve stimulator and a microcomputer unit. The transducer can be fastened to the thumb, and the signal of the thumb movement in response to ulnar nerve stimulation is measured and registered in the computing unit. In clinical practice, it has been proved that this new apparatus can achieve reliable evaluation of nuromuscular transmission function and improve the quality of anesthesia in patients care during surgical operation.