The invention discloses a nonmetal ultrasonic detector verification system. The system is characterized by comprising a motion control and measurement feedback system for driving a transmission transducer and a receiving transducer of a nonmetal ultrasonic detector to make relative movement, and an air acoustic-path adjusting device for fixing the transmitting transducer or the receiving transducer on the nonmetal ultrasonic detector on the motion control and measurement feedback system. Compared with the conventional nonmetal ultrasonic detector vertical method, the system using a closed loop system and an automatic control system can effectively improve the operation reliability and the measurement accuracy; the data is processed by a linear regression processing method, which can comprehensively analyze the measurement error and effectively eliminate the influence of zero sound on the measurement result.