Abstract: Recent earthquake damage investigations found that a large number of reinforced concrete frame buildings were heavily destroyed at beam-column joints and columns， without forming the beam-hinging mechanism expected in the design. Installing reinforced concrete wing walls beside the existing columns remains a fundamental and effective strengthening method， by improving seismic performance of both the columns and the joints， while promoting a beam-yielding mechanism. Two 1/2-scale frame specimens were manufactured， and one of them was strengthened by post-installation wing wall. By quasi-static tests， hysteretic behaviour， deformation capacity， energy dissipation power and failure mode of the two specimens were examined. The results show that the stiffness， bearing capacity and energy dissipation capacity of the strengthened frame were significantly improved. After strengthening， failure mode of the frame was changed from joints shear failure to expected beam-hinging. The efficiency and applicability of wing wall installation method were validated for strengthening existing frame structure buildings with seriously weak beam-column joints.