利用快速傅里叶分析手段对激光焊接稳定过程及出现未焊透缺陷时等离子体的光声信号进行频域分析，发现在焊接过程稳定时，信号的频谱中存在明显线谱，以３００Ｈｚ处为最强。在出现未焊透缺陷时，光声信号的频谱为连续谱，无明显线谱。这为提高缺陷监测精度提供了一条新途径。 The fast Fourier analysis of the laser welding process and welding imperfections appeared in the plasma photoacoustic signal frequency domain analysis found that the welding process is stable, the signal spectrum there is a clear line spectrum at 300Hz at The strongest In the presence of impermeable defects, the photoacoustic signal spectrum is continuous spectrum, no obvious line spectrum. This provides a new way to improve the defect monitoring accuracy.