Abstract: To study the variation law of ultrasonic nonlinear response characteristics at the contact interface of high-voltage cable terminals, the morphology of the contact surface of the silicone rubber stress cone and the stress-strain relationship of the material are measured. A simulation model for ultrasonic detection of the silicone rubber contact interface is established, and an ultrasonic nonlinear detection test system is built. Ultrasonic detection experiments are conducted to verify the correlation between interface pressure and ultrasonic nonlinear coefficient, and to explore the causes of nonlinear response at the contact interface. The results show that the nonlinear response of the contact interface comes from the material nonlinearity and the nonlinearity of the contact interface, and the high-order harmonic components of the echo signal are mainly due to the nonlinearity of the contact interface. As the interface pressure increases, the relative increase of the ultrasonic nonlinearity coefficient gradually decreases from 25.10% to 1.60%. The decrease of the amplitude of fundamental wave is 1.89%, 1.75%, 1.84%, 5.22%, 4.73%, 0.94%, and 14.38%, respectively. The trend of the second harmonic is similar to that of the fundamental wave. As the interface pressure increases, both the amplitude of the fundamental wave and the amplitude of the second harmonic show a decreasing trend. The simulation results and experimental results mutually confirm each other, further providing reference for the feasibility of engineering application of ultrasonic nonlinear detection method in pressure detection of high-voltage cable terminal interface.