The invention discloses a powder metallurgy brake shoe structure and a machining method thereof. The brake shoe structure comprises a back plate, a steel backing, a friction body and a shoe back component. The back plate is fixed to the arc in the shoe back component, the steel backing is located on the inner arc of the back plate, and the friction body is fixed to the steel backing. The shoe back component is composed of a shoe back body, arc check blocks, boss locating pins and a curved shoe nose, the arc check blocks, the boss locating pins and the curved shoe nose are arranged on the shoe back body, and the arc check blocks, the boss locating pins, the curved shoe nose and the shoe back body are integrated. A weld joint formed by welding the steel backing and the shoe back body on a brake block in the middle of a brake shoe is connected with weld joints formed by welding the steel backing and the shoe back body on brake blocks on the two sides of the brake shoe into a whole, the situation that in the frequent brake process of a currently-used shoe brake on a locomotive, weld joints of welding parts crack, and especially weld joints crack and even fall off in the welding process of a shoe brake nose on the brake shoe can be avoided within the service life of the shoe brake, and potential running safety hazards are eliminated.