Plasma arc cutting is a thermal cutting method that melts and removes the material by projecting an arc heat source onto the cutting part of material. In the case of cutting thick plate, plasma arc piercing is performed before plasma arc cutting for cutting quality and cutting efficiency. The quality of plasma arc piercing varies greatly depending on several variables. In particular, the factors such as stand-off distance, current and thickness of material play an important role in inducing double arcing. Therefore, it is necessary to investigate the phenomenon that occurs during plasma arc piercing according to the factors. In this study, we synchronized the arc shape photographed with a high-speed camera using a band-pass filter and the voltage waveform measured with the DAQ equipment. And it was confirmed that the smaller the stand-off distance, the stronger the current and the thicker the thickness of material, the worse the top surface of the material by double arcing.