Orbital electromagnetic launch technology has broad prospects in the fields of military, industry and transportation due to its advantages of fast launch speed, short start-up time and large launch kinetic energy, realizing the maximum utilization of electromagnetic energy. In order to improve the service life and reuse rate of the orbital electromagnetic launch device and solve the positioning problem that is prone to ablation during the launch process, this article first established the equivalent circuit and discharge equation of the orbital electromagnetic launch device and theoretically analyzed its heat primary sources. Based on this, a finite element model of electromagnetic and thermal multi-field coupling is established, and the distributions of the electromagnetic field and temperature field during the launch process are simulated. It is concluded that the current density and magnetic induction intensity are concentrated at the armature groove and tail fin and around the contact points between the armature and the slide rail, and the heat is concentrated at the armature groove and slide rail. These areas are the parts where ablation damage of electromagnetic launch devices is prone to occur. It provides simulation-level guidance for the next step of manufacturing and testing of electromagnetic launch devices.