To reinforce the connections of angle diagonal braces of power transmission towers, retrofit methods attaching the additional steel plates including adhesive bonding are proposed. Comparing to the bolt attachment, adhesive bonding attachment can add the additional plates without the loss of sectional area. In this paper, real-size mock-up tests and finite element analysis for the reinforced connections are carried out and it is confirmed that adhesive reinforcement reduces the damage concentration around the existing bolt holes of angle member and improves deformation performance of brace and ultimate strength of connections.