The present invention discloses a high-sound-absorption composite material for a traffic sound barrier. The surface of a porous sound-absorption material layer is clad with a cladding layer in a sealing way, and the clad parts and joints are in sealed connection. The cladding layer is an expanded polytetrafluoroethylene microporous membrane or a modified membrane of the expanded polytetrafluoroethylene microporous membrane. A preparation method is disclosed, comprising the following steps of preparing a porous sound-absorption material and the expanded polytetrafluoroethylene microporous membrane or the modified membrane of the expanded polytetrafluoroethylene microporous membrane before processing; cutting the porous sound-absorption material; covering the surface of the porous sound-absorption material with the expanded polytetrafluoroethylene microporous membrane or the modified membrane of the expanded polytetrafluoroethylene microporous membrane; performing sealed connection on the clad parts and joints; testing the composite material and packaging the qualified composite material. By the above approach, the present invention is able to greatly reduce noise, has a soundproof function and a better sound-absorption function, has a prolonged service life, and features environmental protection, flame retardancy, damp-proofing and high plasticity.