Molded case circuit breaker

A molded case circuit breaker comprises an upper cover, a circuit breaker assembly and a lower cover, a positioning part is connected between the upper cover and the lower cover, the positioning part comprises a positioning groove arranged on the lower cover, a positioning plate with the other end installed on the upper cover is clamped in the positioning groove, an extension part is arranged on the inner wall of the positioning plate, the extension part is connected with a clamping part, and the clamping part is connected with the circuit breaker assembly. The upper cover is provided with a clamping groove used for being clamped with the extending part, the positioning plate and the upper cover are clamped with the lower cover through the extending part and the clamping part and then are clamped and positioned, the positioning precision between the upper cover and the lower cover can be improved by additionally arranging the positioning plate, and a gap generated after the upper cover and the lower cover are