The invention discloses a rapid identification method for the power transmission line fault location of the most severe transient power angle stability, and belongs to the technical field of power system operation and control. Existing power transmission line fault transient power angle stability analysis is established on the basis of the assumption that the power transmission line fault location of the most severe transient power angle stability is only arranged at the two ends. If the fault location of the most severe transient power angle stability is arranged in the middle of the power transmission line, the power system operating based on the transient power angle stability analysis result of the assumption has safety hidden trouble. The change law of the index of similarity between transient power angle stability dominant modes for the situation that the power transmission line fault is located at different positions is analyzed, and the power transmission line fault location of the most severe transient power angle stability is rapidly identified through combination of a dichotomy and a quadratic curve fitting method of transient power angle stability margin of the situation that the power transmission line fault is located at different positions. The method can be used for operation mode planning of the power system and can also be used for safety and stability online defense of the power system.