The simulation of Internal Electro Magnetic Pulse(IEMP) coupling with Electro Magnetic Pulse(EMP) coupling in sealed cavity without space charge limit is described in detail. The research of coupling models contains magnetic field coupling to cable，electric field coupling to cable, charge or radiation coupling on the surface of cable. The voltage source and current source in the lumped parameter equivalent circuit are adopted to express the theoretical models of electric field coupling，magnetic field coupling and charge coupling. The space charge current and space charge density are distribution function dependent on space and time. The current and field induced by the IEMP coupling of charged cable and space charge are researched；the influence of the trends, types, bias and terminal loads of the cable，are observed. The test and theoretical results are obtained.