Abstract: As the characteristics of linear ultrasonic response to the invisible impact damage in carbon fiber reinforced polymer (CFRP) composite laminate are so weak, a nonlinear ultrasonic Lamb wave detection method for determining the low-energy impact damage in the CFRP laminate is proposed. First of all, build a platform for nonlinear ultrasonic Lamb wave detection, propose a means for Lamb wave excitation and analyze its modal composition. Secondly, determine whether each model meets the testing conditions required by the nonlinear ultrasonic Lamb wave detection method. Finally, analyze the sensitivity of linear and nonlinear ultrasonic detection characteristics to the damage, and propose the nonlinear feature parameters for detecting invisible impact damage.. The research results show that the relatively nonlinear coefficient is highly sensitive to the low-energy (3 J and 5 J) invisible impact damage, which can be applied in non-destructive detection of this kind of damage.