Due to the potential burn damage between the armature and the rails during the launch process of the electromagnetic railgun, which can lead to a decrease in system performance or even launch failure, it is essential to investigate the forces on the armature and rails, as well as the distribution of multiple physical fields during the launch process. A modular modeling approach has been adopted to establish a mathematical model of the electromagnetic railgun, and a simulation analysis has been conducted considering the output characteristics related to the forces acting on the armature. Using COMSOL, a multi-physics coupling simulation was performed. By examining the distribution of current density, magnetic field strength, and temperature field within the electromagnetic railgun in conjunction with the force conditions of the armature during motion, it was found that in the initial motion phase, rail wear is primarily caused by armature-rail frictional heat and contact resistance Joule heat. In the later motion phase, severe rail ablation occurs mainly due to electric contact arcing between the armature and the rails. This research into the erosion mechanism of electric contact arcing under the influence of electromagnetic thermal multi-field coupling has significant implications for improving the reusability and lifespan of electromagnetic launching devices.