Abstract: To keep good interfacial contact between the sliding armature and the two electrodes of electromagnetic rail thruster, the electrode spacing should fluctuate within an allowable range under the impulse force generated by pulse current. A transient coupled model of the electrodes and their bracing structures is built by time-varying field theory and transient dynamics equation. The distributions of parameters of transient electromagnetic field are analyzed, and the dynamic response parameters of the electrodes and their bracing structures are obtained. The simulated results show that the epoxy bracing structures have good cushioning capacity to resist the impulse force generated by pulse current; the bracing material with low elastic modulus is more easily vibrated at the rising and peak phases of pulse current, and the vibrated deformation has little effect on the electrode spacing.