The invention provides a brake drum assembly structure. The brake drum assembly structure comprises a brake drum, friction plates and brake shoes; a rotating shaft fixed block is fixedly mounted on the inner side of the bottom of the brake drum; two pistons are movably and symmetrically mounted on the inner side of a hydraulic cylinder; one sides of the tops of the two brake shoes are tangential to one sides of the two pistons; and the friction plates are fixedly mounted on the outer sides of the brake shoes through rivets. Through arrangement of the friction plates and the brake shoes, the use safety is facilitated; and when the friction plates of the device are installed, square projections on one sides of the friction plates are totally embedded in square grooves on one sides of the brake shoes, and then, the rivets penetrate through the square projections on one sides of the friction plates through one sides of the friction plates to embed in the inner sides of the square grooves on one sides of the brake shoes, so that the friction plates can be firmly fixed, the transverse and longitudinal friction force between the friction plates and the brake shoes can be effectively increased, the deviation of the friction plates in use can be effectively prevented, and excellent brake effect is guaranteed.