Abstract: The paper analyzed working principle of phase-controlled and magnetic bias arc-suppression coils, introduced characteristics of compensation current of the two arc-suppression coils in details and expounded working characteristics of the two arc-suppression coils when power grid is in state of normal running and single-phase grounding fault. The results are as following: phase-controlled arc-suppression coil with filtering circuit has certain filtering function and bad compensation effect because of filtering function; magnetic bias arc-suppression coil not only can filtering effectively but also has good compensation effect.