Abstract: Breakdown characteristics of a gap breakdown load was investigated in this study, and a Reversely Switched Dynistor (RSD) discharge circuit was designed based on the load. Based on the characteristics of the load the RSD discharge circuit was improved and optimized. The volume of the magnetic switch was reduced. To protect the thyristor and RSD, a diode was anti-parallely connected with the thyristor, which reduced the time requirement when a power voltage was applied to RSD. Experimental results show the circuit designed in this study can switch a high voltage and high current smoothly, and allows the power voltage to change in a wider range.