Abstract: With the penetration of inverter-interfaced distributed generators (IIDGs) raised, the fault characteristics of distributed network have also changed. Affected by the current limiting of power electronics and converter control strategies, the amplitude of fault current is weakened and the characteristics of fault become complex, rendering traditional protection schemes potentially. Hence, this paper proposes a line protection scheme of distribution network based on additional harmonic current. Based on the flexible and controllable characteristics of the IIDGs, the proposed method actively injects a harmonic current signal into the protection system after a fault by changing the amplitude limiting control of IIDG. Meanwhile, considering the influence of this harmonic signal on the control of IIDG, a corresponding filter is designed. Further, a new protection criterion is constructed based on the amplitude of this harmonic current signal and its phase relationship with the protection positive sequence measurement voltage. A 10 kV active distribution network case study is simulated in PSCAD/EMTDC, and the results verify that the proposed protection scheme can operate correctly and rapidly under both symmetrical and asymmetrical faults.