The invention discloses a method and structure for reinforcing an original concrete bridge. The method comprises the following steps of a, removing the foreign matters and the attachments from a to-be-reinforced region so as to expose a new surface of a concrete structure; b, machining the corresponding steel bar embedding holes; c, machining the corresponding reinforcing ribs, wherein each reinforcing rib comprises a first end part, a second end part opposite to the first end part and a connecting part connected with the first end part and the second end part, and the first end parts and thesecond end parts of the reinforcing ribs are fixed in the corresponding steel bar embedding holes; d, coating the permeable polymer mortar on the concrete surface of the area to be reinforced of the original bridge; e, providing a template, coating the inner surface of the template with a layer of release agent, and fixing the template to a preset position to locate the permeable polymer mortar inthe template; and f, after the permeable polymer mortar is hardened, removing the template. According to the present invention, the bearing capacity of the bridge is effectively improved, the cost islower, and the construction period is short.