The arc behavior in dry hyperbaric Gas Metal Arc Welding (GMAW) process was investigated by using a high speed camera system and welding electric signal acquisition system. The arc shape in hyperbaric argon environment of 0.1-2MPa shows quite different characteristic from that at normal pressure. With the increase of ambient pressure, the arc length turns shorter, arc column is contracted, and the arc brightness increases. At elevated ambient pressure, the arc length increases with increasing welding voltage. Arc voltage has a good linear relation with arc length. The sum of the fall voltages at ambient pressure of 0.4MPa, 0.8MPa, and 2MPa is nearly constant which is about 20.2-21.7V. The values of electric field strength of arc column at different ambient pressure were gained through the linear fit, which are increased with increasing ambient pressure. The arc static characteristics at elevated ambient pressure are raising characteristics, and it is shifted upward with increasing ambient pressure.