In the process of electromagnetic rail launch, due to the interference fit between the armature and the rail and the rough contact surface, friction and wear will occur, resulting in the lack of material on the contact surface of the armature and rail, resulting in uneven distribution of current at the contact surface, so that the concentrated current causes the arcing phenomenon of the contact surface and further leads to ablation and wear, affecting the efficiency and reliability of the armature and projectile launch. In this paper, based on molecular dynamics simulation, the armature-orbit friction model of electromagnetic railgun is established by LAMMPS. The friction of armature surface in the process of relative friction between armature and rail is explored from the micro level, and the influence of armature interference parameters on friction, friction coefficient and number of wear atoms is discussed. It is proposed that it is sufficient to make the armature overload just enough to provide the initial contact force required at the initial moment of the EM railgun launch.