High-accuracy respiratory monitor

Provided is a high-accuracy respiratory monitor. A processor controls a wave generation circuit to generate alternating current signals with a certain frequency. After amplifying of a drive circuit and impedance matching, the alternating current signals drive an ultrasonic wave transmitting probe to transmit a length of ultrasonic wave. The time when the ultrasonic wave is transmitted is T0. The starting time of echo of the ultrasonic wave is determined by using a reversed-phase echolocation method. The time interval between the time when the ultrasonic wave receiving probe receives the signals and the time when the ultrasonic wave transmitting probe transmits the ultrasonic wave is t. Time offset delta t is measured according to experience. At present, the distance can be calculated through the following formula: L= (Tr-T0-delta t)*v/2, wherein delta t is a fixed value and can be measured according to experience, and V is sound velocity.