The invention discloses a presplitting drum brake, which comprises a drum brake body which is molded by casting, wherein the drum brake body comprises a mounting part and a braking part; a transition connection part is arranged between the mounting part and the braking part; a crack which penetrates through the wall thickness of the braking part is arranged on the braking part; the crack extends from one end part which is far away from the transition connection part to the transition connection part; a plurality of steel hoops which are axially arrayed and are in interference fit with the braking part sleeve the periphery of the braking part. The drum brake body is presplit by the crack to form an elastomer, the stress effect is improved, and the resistance buffering impact force is enhanced; meanwhile, the drum brake body only bears the rotation friction braking force; when the drum brake body is heated and strong tension force acts, the crack is capable of eliminating the expansion stress in time, and the fracturing phenomenon is reduced. The brake tension force is borne by the steel hoops, and the strength of extension and the anti-deformation rigidity of the drum brake are enhanced. Due to the adoption of the drum brake, the structural intensity and the mechanical performance are improved, the service life of the drum brake is prolonged, the radiating performance is good, and the use safety is high.