The invention discloses an old T-shaped beam bridge steel wire rope MPC composite shear-resistant reinforcement structure and a construction method thereof. As for old T-shaped beams, diagonal cracksare form in the positions, close to one fourth of the sections, of the beam ends of the old T-shaped beams, so that the shear-resistant bearing capability does not meet the current traffic volume requirement; angle-form positioning steel plates are anchored and bolted on the surfaces of web plates on the two sides of the old T-shaped beams; a high-strength steel wire rope is anchored between everytwo angle-form positioning steel plates, and an MPC material reinforcing layer is cast between every two angle-form positioning steel plates on the two sides of the corresponding old T-shaped beam; one ends of expansion bolts are anchored in concrete in the web plates of the old T-shaped beams, and the other ends of the expansion bolts are anchored on the surfaces of the angle-form positioning steel plates, so that the effect that the angle-form positioning steel plates are fixed is mainly achieved; and an embossing anchorage device is used for anchoring each steel wire rope on the corresponding angle-form positioning steel plate. The construction method is used for shear-resistant reinforcement of an old T-shaped beam bridge, the reinforcing structure is simple, the engineering construction quality is easy to ensure, force performance is good, the reinforcing effect is obvious, construction is convenient and rapid, the requirements for machine tools and equipment needed by construction are low, and popularization is easy.