A superconducting magnetic energy storage (SMES) system has many advantages such as high storage efficiency and quick response to load fluctuation. However, the system contains the possibility of various failures, which are mainly generated from by a transition to normal conducting state. These system failures tend to result in arc discharge inside the system which gives a serious damage to the entire system. Based on above considerations, a superconducting pulsed power system (SPPS) with a mechanical opening switch as an energy transfer switching device was designed to clarify the electrical insulation problems of the superconducting magnet. In this study, the characteristics of internally induced voltage of the magnet during system discharge were investigated. Especially, generation mechanism of the oscillating waveform which appears between magnet terminals just before arc extinction was analyzed using the digital simulation program EMTP (Electromagnetic Transients Program) considering distributed constant circuit of superconducting magnet, load condition and time varying arc resistance of the switch. The experimental and theoretical investigations showed that the voltage waveform was strongly influenced by the load condition and arc discharge triggered by the switch operation. Finally, a suppression method of the oscillating surge is proposed based on the theoretical consideration.