Abstract: In view of shortages of refuse action or delay of traditional leakage protection device under fault of power distribution network, a fault isolation device of distribution network was designed. Inductance and adjustable capacitor in parallel are used to design impeder of the device, and coupling voltage generated by additional winding of the impeder to drive control system to switch adjustable capacitance rapidly, so as to realize on-line adjustment of isolation parameters accurately in fault condition. The simulation and experimental results show that the isolation device can offer high impedance, isolate fault point effectively, and guarantee safe and reliable operation of the distribution network when the power distribution network occur single-phase fault.