The present invention discloses a fast power swing unblocking method and apparatus for a distance protection in a power system, which is able to ensure fast phase-segregated tripping of distance protection for faults during a power swing (3-phase or 2-phase swing). The power swing unblocking method in a power system according to the present invention comprises calculating changing rates of impedances for all operating loops of the distance protection in the power system; and determining a fault loop based on the calculated changing rates. If there is a fault loop, a blocked distance zone for the fault loop is unblocked. Before calculating the changing rates, whether the power system is under a power swing is checked and a distance zone that might mal-operate under the power swing is blocked if it is checked that the power system is under the power swing. By applying this invention, the performance of the distance protection during power swings can be improved, and the distance protection can ensure faster and phase-segregated operation, which are very beneficial for the system reliability.