We have developed personal computer simulation of arc behavior and bead appearance for Gas shielded Metal Arc Welding(GMAW). This arc simulator is related to software technology for welding automation. The simulator system consists of a personal computer, an original control box, computer boards, and connecting cable. When a welding condition is set via the control box or key board, the system simulates and displays the image of arc behavior and bead appearance in real-time on the computer monitor. The main function of the simulator is to provide some messages that inform the user whether simulated arc behavior is correct or not, conditions, we can better understand the relationship between arc behavior and welding conditions Therefore, the effect is to significantly improve welding skills.