<p>The electromagnetic launcher, such as a railgun, operates under extreme conditions of the strong pulsed currents, rapidly varying magnetic fields, high sliding velocities, and high temperatures. The uniform physical field is generally assumed for two-dimensional model in the width direction or the length direction of the rail, however, it will inevitably cause significant computational errors for each physical field. Therefore, the three-dimensional electro-magneto-thermo-mechanical coupling model for the electromagnetic launcher is considered in this paper. The three-dimensional distributions of magnetic flux density, temperature and deformation on the rail can be provided quantitatively by the finite element method with accounting for the coupling factors of electromagnetic force, Joule heat, thermal stress, temperature-dependent conductivity, and frictional heat. The results of electromagnetic field, thermal field and deformation field indicate that the three-dimensional model not only captures the trends of variation in various physical fields but also has higher numerical accuracy in all scenarios compared to the two-dimensional model. In addition, when using an air domain size of 0.1&#xa0;m and a mesh size of 6.67&#xa0;mm along the length direction of the rail, the computational cost and convergence have a good balance. These results will provide the theoretical basis for the engineering design and application of electromagnetic launchers.</p>