The quality laser cutting of thick sheet metals is demanding due to requirements of high precision, lost cost, and short processing time. However, the surface plasma is formed during the cutting process to influence the end product quality. The surface plasma is transiently hot and lowers the resulting cutting quality via increasing thermal erosions from the cut edge edges. In the present study, the surface plasma characteristics are examined using the Langmuir probe. Electron temperature and electron number density are determined in the surface plasma. The cutting quality is, then, related to the plasma characteristics. Scanning Electron Microscopy (SEM) is carried out to examine the microstructural changes at the cut edges. It is found that cutting quality improves at a particular assisting gas pressure; in which case, the influence of surface plasma on the cutting process becomes the minimum.