The invention relates to a beam strengthening method. The method comprises the following steps: firstly, chiseling a beam top anchorage groove on the top surface of a beam end, obliquely boring along the direction of two sides of a beam rib, and paving a positioning groove for fixing a prestressed steel wire buddle and a positioning tension sleeve along a beam web; mounting an anchorage plate;
polishing the lateral surfaces and a bottom surface of a beam, and roughening a strengthening surface; mounting the steel wire buddle and the tension sleeve, namely arranging the positioning tension sleeve in the positioning groove of the positioning tension sleeve, threading the steel wire buddle from the anchorage plate at one end of the beam, placing the steel wire buddle into the positioning groove, then threading out the steel wire buddle from the anchorage plate at the other end of the beam, tightening the steel wire buddle and temporarily fixing the steel wire buddle by a rolling anchorage head; tensioning the steel wire buddle by using a tensioning jack or a
winch at one end of the steel wire buddle, anchoring the steel wire buddle when reaching a design value, and then
casting and sealing the wire buddle by concrete; implanting a pin into a beam body; after positioning and setting out a reinforcing
steel bar on the beam body, binding reinforcement mats on the surface of the beam, and partially spot-
welding the reinforcement mats; painting an interface agent; and plastering composite
mortar. The method is active, ultra-strong and durable, can well overcome the main defects of the prior strengthening technology, and has strong effectiveness and economy.