Abstract: To extend the switch lifetime by minimizing electrode erosion, rotary arc gapswitches (RAG) were proposed. The rotation of the arc can be achieved by providing an external rotating magnetic field from outside or by self-induced magnetic field. Since the railgap switch has the advantages of low impedance, long burn-out life, wide operating range and low jitter time. Combining the RAG and rail-gap together, a switch were designed, and the characteristic of the switch has been studied by experment. The switch has low jitter and wide operating voltage range. The results indicate that the RAG switch employing a sharp knifeedge electrode as a third trigger electrode can distinctly reduce the electrode erosion and prolong the lifetime. The surface conditions and photomicrographs of the elec