Abstract: It is necessary to establish reliable quantitative techniques for nondestructively evaluating and characterizing the materials in order to ensure the safe use of the component. The use of the nonlinear characteristic can solve some problem that linear ultrasonic testing technology is difficult to solve. With intensive research, now nonlinear ultrasonic detection method is having the incomparable advantages of linear ultrasonic testing in closed crack detection, adhesive strength assessment of adhesive structure, mechanical property degradation evaluation, etc.