The invention discloses a fabricated mortise and tenon reinforcing system used for H-type steel. The fabricated mortise and tenon reinforcing system comprises reinforcing bottom plates, L-shaped innerplates and L-shaped outer plates. The reinforcing bottom plates are closely attached to a web plate of the to-be-reinforced H-type steel. Dovetailed tenons are arranged on the outer sides of the bottom plates. The reinforcing bottom plates and the L-shaped inner plates are connected through dovetail joints. The L-shaped inner plates and the L-shaped outer plates are arranged on the inner side andthe outer side of the flange of the to-be-reinforced H-type steel and are connected through bolts. The two adjacent L-shaped outer plates on the outer side of the flange are connected through bolts,and the to-be-reinforced H-type steel needs the two reinforcing bottom plates, the four L-shaped inner plates and the four L-shaped outer plates. The fabricated mortise and tenon reinforcing system has the advantages that all fabricated construction is achieved, operation is simple and high in efficiency, and the reinforcing effect is obvious. The fabricated mortise and tenon reinforcing system can be widely applied to design or reinforcing modification of H-type steel components, the reinforcing method suppresses transverse deformation of the components, and therefore the aim of improving thebearing capacity of rod parts is achieved.