The invention provides a structure and method for strengthening a reinforced concrete frame pillar, and belongs to the technical field of constructional engineering. When the reinforced concrete frame pillar serves as a center pillar, longitudinal hollow square steel tubes which are equal in vertical length are arranged on the periphery of the frame pillar, at least one group of horizontal connecting ribs is arranged between the longitudinal hollow square steel tubes on the two adjacent sides of the frame pillar, cast-in-place reinforced concrete forms a cross-shaped wing wall, and the cross-shaped wing wall and the frame pillar are integrated. According to the structure and method for strengthening the reinforced concrete frame pillar, the hollow square steel tubes and the pillar are connected through expansion bolts and are stressed together, and therefore shearing resistance, bending resistance and overall lateral stiffness of an original frame pillar are improved. In addition, the construction material is easy to obtain, the construction method is simple, the construction period is short, economic benefits are good, the universality is high, and the structure and method for strengthening the reinforced concrete frame pillar are suitable for strengthening of frame pillars in reinforced concrete structures and frame shear wall structures.