The electromagnetic launch system has a complex structure with intense multi-physical field coupling effects. Different armature-rail combinations can have varying impacts on the launch performance. This study establishes three types of armature-rail structural models with different contact forms: flat, convex, and concave rails paired with C-type armature. It focuses on analyzing the “electro-magnetic-thermal-mechanical” multi-field coupling phenomena in electromagnetic railgun systems and the influence of armature-rail contact forms on system performance. The conclusions are as follows: The concave armature-convex rail contact form exhibits better performance in interface thermal characteristics and the lowest stress.