The invention belongs to the technical field of reinforced concrete beam reinforcing, and discloses a reinforcing structure and reinforcing method. The reinforcing structure comprises a longitudinal steel plate and carbon fiber cloth strips, the longitudinal steel plate is pasted to the bottom face of a reinforced concrete beam, the carbon fiber cloth strips are pasted on the outer sides of the reinforced concrete beam and the longitudinal steel plate. The reinforcing method comprises the following steps that A, according to the specification of the reinforced concrete beam, longitudinal reinforcing bars are equivalently replaced by the longitudinal steel plate, hoopings are equivalently replaced by the carbon fiber cloth strips, a sectional area of the steel plate to be pasted and a sectional area of the carbon fiber cloth strips to be pasted are calculated; B, the longitudinal steel plate and the carbon fiber cloth strips with the corresponding sizes are designed and processed according to the sectional area of the steel plate and the sectional area of the carbon fiber cloth strips; C, the longitudinal steel plate is pasted on the bottom face of the reinforced concrete beam; and D, the carbon fiber cloth strips are pasted on the outer sides of the reinforced concrete beam and the longitudinal steel plate. Through cooperating arrangement of the longitudinal steel plate and the carbon fiber cloth strips, influence on using space is little, and the whole construction procedures are simple and efficient.