Positive-sequence polarized voltage of distance relay is discussed with voltage phasor diagram method. The phase angle variation of bus voltage and bus positive-sequence voltage before and after the various asymmetrical faults for long-distance and heavy-load lines are analyzed and compared. The bus positive-sequence voltage is adopted as polarized voltage of distance relay， which can effectively reduce and avoid overreach of distance relay when the grounding fault via fault resistance occurs near the setting point of the distance relay.