提出一种无源电检测装置，对A304不锈钢YAG激光焊接过程中的等离子体电信号进行检测，并利用高速摄像机对等离子体的形态进行观察。结果表明，不同焊接模式下的等离子体电信号具有不同的时域特征。对不同焊接模式下的等离子体电信号特征进行理论与试验分析，发现等离子体电信号受等离子体效应和鞘层效应的共同影响;小孔的形成与否是造成不同焊接模式下等离子体电信号特征不同的决定性因素。

A novel passively electrical device is proposed to detect the electrical signals of plasma in YAG laser welding of A304 stainless steels and a high-speed camera is used to observe the plasma shapes. The results indicate that the time-domain characteristics of signals are different in different welding modes. The theoretical and experimental analyses of the signal characteristics under different welding modes indicate that the plasma electrical signal is influenced by the combination of the plasma effect and sheath effect; the determinant factor resulting in different electrical signal characteristics under different welding modes is whether the keyholes are formed or not.