Abstract: In order to improve the detection capability of nonlinear ultrasonic technology and optimize the experimental settings, a method to determine the testing resolution and sensitivity of nonlinear ultrasonic testing systems was proposed, and the experimental system was set up according to this method. The nonlinear ultrasonic measurements based on the method of second harmonic generation were carried out for several specimens which had same material but different thicknesses. Then, the relative nonlinear parameters of the specimens were linear fitted with the specimen thicknesses. It was found that the ratios of the slopes and intercepts of the fitting curves could be used to quantify the testing resolution of the testing system, and the slopes can be used to characterize the testing sensitivity. The results showed that the instrument nonlinearity introduced by nonlinear ultrasonic testing systems can be removed by using this method, which enhanced the contrast ratio of the measurement data. Therefore, the evaluation of material damage degree and microstructure evolution based on nonlinear ultrasonic technology can be carried out more efficiently.