The invention belongs to the technical field of mechanical equipment and relates to a waste motor vehicle tire breaking device. A bent feeding channel is mounted above a breaking device; a feeding hole is formed above a transverse feeding channel; a push block is arranged in the transverse feeding channel; a reciprocating push device is mounted on the outer side of the push block; the breaking device comprises a first breaking chamber and a second breaking chamber; the second breaking chamber communicates with the first breaking chamber and positioned below the side of the first breaking chamber; a cylindrical first breaking cavity is formed in the first breaking chamber and communicates with the feeding channel; a first rotating disc which is rotationally connected in the first breaking chamber is arranged at a central position of the first breaking cavity; first breaking knives are uniformly distributed in a peripheral direction of the first rotating disc; two first discharging holesare formed in the lower part of the first breaking chamber; the structure of the second breaking chamber is similar to that of the first breaking chamber; a vibrating screen is arranged below the first breaking chamber. The problems that the conventional waste tire breaker is low in breaking efficiency and high in operational energy consumption are solved.