Abstract—Since DC current interruption by vacuum circuit breaker (VCB) seems difficult, new method such as external magnetic field application should be developed for DC current interruption. The objective of this work is to study DC vacuum arc under external rotating transverse magnetic field. In the experiments, the arc current was in the range of 100-300 A. The current of two tank circuits (each circuit includes two Helmholtz coils and a capacitor) operated 90° out of phase to produce a rotating magnetic field. The rotating magnetic field strength was adjusted by the charging voltage of capacitor in the range of 0-30 mT. The frequency of rotating magnetic field was set from 200 to 800 Hz by adjusting capacitance of capacitor. In the experiments, the arc voltage under different rotating magnetic field was recorded by oscilloscope. The research can help improve DC vacuum arc voltage and develop interruption capacity of DC vacuum circuit breaker.