The invention provides a diesel locomotive body and a diesel locomotive. The diesel locomotive body comprises a carriage and a top cover, wherein a first annular supporting frame is fixedly and vertically arranged at the periphery of an opening, a first seal ring is arranged on the first annular supporting frame, a second annular supporting frame is fixed to the lower surface of the top cover, and a second seal ring is arranged on the second annular supporting frame; the carriage is also provided with a pressing device and a tensioning device, and the opining is positioned between the pressing device and the tensioning device; the pressing device comprises a first stud, a first nut and a press block; the tensioning device comprises a second stud, a second nut and a fixed base; one side of the top cover is hinged to the upper end part of the second stud. According to the diesel locomotive body, improvement on sealing reliability of the detachable cap installed on the top of the locomotive is achieved, and operation safety of equipment in the locomotive is improved.