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This paper proposed three composite strengthening methods for repairing seismic‐damaged RC frames to restore their seismic capacity. Combined with the damage characteristics and failure mode of the frame under the earthquake action, the local strengthening of the column adopts the angle steel and gusset plate, and then the whole frame is strengthened by the inclined brace, the thin‐walled steel plate and the V‐shaped buckling restrained brace (BRB), respectively. Through the cyclic loading test, the main seismic indexes of the strengthened specimen, including hysteresis curve, skeleton curve, ductility, energy dissipation capacity, and stiffness degradation, are studied. The influence of different strengthening methods on the seismic performance of the seismic‐damaged specimens is analyzed. The results show that the seismic performance of strengthened specimens is significantly improved, and the bearing capacity, ductility, and energy dissipation capacity are increased by 2.58–5.57, 1.05–1.24, and 7.67–15.87 times, respectively. The thin‐walled steel plate shear wall and the inclined brace are destroyed at first during loading to effectively delay the premature destruction of the main frame. The composite strengthening method makes the original frame realize the failure mechanism of “strong joint weak member, strong column weak beam” under strong earthquake action. The strengthened specimen satisfies the seismic requirement and has good seismic performance. The seismic performance of the frame strengthened with the V‐shaped BRB is better than that of the other two strengthening methods. Based on the test date, the formula for calculating the shear‐bearing capacity of the beam end is presented.