In order to study the action mechanism of magnetic field of a coil to restraint deformation of a shaped charge jet (SCJ), the theoretical models of magnetic flux intensity distribution, induced current density distribution and electromagnetic force density distribution in a SCJ under the action of pulse magnetic field of a magnet exciting coil were proposed. The finite element (FE) model for the coil to restraint deformation of SCJ was established considering the electromagnetic-temperature-structure multi-physical field coupling analysis. The FE analysis results were verified with tests. The results showed that SCJ can be effectively restricted by the magnetic field of the coil; electromagnetic force doing work and Ohmic heating effect’s cumulation make SCJ generate effective deformation and become more uniform; the fracture process of necking down part of SCJ can be delayed, and the penetrating capacity of high explosive anti-tank cartridge can be enhanced.