Abstract: The non-linear coefficient is measured by the PZT chip-probe penetration method. The measurement data has poor repeatability. In this paper, a pressure monitoring and clamping device for measuring the nonlinearity of materials in RITEC RAM-5000 SNAP nonlinear high-energy ultrasonic testing system is designed. It can realize the real-time monitoring of the bonding force of materials, improve the speed of point-by-point measurement and reduce the interference of the coupling conditions on the measurement results. The results show that the device can greatly improve the sensitivity of ultrasound to micro-defects, and enhance the penetration rate of ultrasound and the accuracy of pore detection.