Abstract: In order to study the equivalence between the coupling amount of the wire to the spherical wave and the coupling quantity under the irradiation of the plane wave, the equivalent conditions of the spherical wave and the plane wave are derived under the assumption of small size of electricity. Under the condition of no equivalent tests, the electromagnetic pulse simulator of the horizontal polarized radiation wave of threat level is used to carry out the cable irradiation experiments, and the induced current under the radiation of spherical wave and plane wave is calculated and compared with the measured waveform, respectively. The results show that the calculation results of spherical wave are closer to the measured waveform. By changing the cable length, the effect of length on the equivalence of two wave propagation modes is obtained in numerical calculation.The results show that when the cable length meets the equivalent conditions, the calculated results are not different. When the equivalent condition is not met, the induced current under the spherical wave is significantly larger than the induced current under the plane wave with the increase of the cable length due to the change of the ECL (effective coupling length) of the cable. The results can be used as a reference for the test setup of electromagnetic pulse effect test in horizontal polarization simulator.