We analyze the effect of second-harmonic generation (SHG) of primary Lamb wave propagation in a two-layered composite plate,and then investigate the influence of interfacial properties on the said effect at low frequency.It is found that changes in the interfacial properties essentially affect the dispersion relation and then the maximum cumulative distance of the double-frequency Lamb wave generated.This will remarkably influence the efficiency of SHG.To overcome the complications arising from the inherent dispersion and multimode natures in analyzing the SHG effect of Lamb waves,the present work focuses on the analysis of the SHG effect of low-frequency dilatational Lamb wave propagation.Both the numerical analysis and finite element simulation indicate that the SHG effect of low-frequency dilatational Lamb wave propagation is found to be much more sensitive to changes in the interfacial properties than primary Lamb waves.The potential of using the SHG effect of low-frequency dilatational Lamb waves to characterize a minor change in the interfacial properties is analyzed.