The invention provides a complete-discharge compression type axial plunger pump or a motor, and relates to the field of axial plunger pumps or motor devices in hydraulic machinery. The complete-discharge compression type axial plunger pump or the motor comprises a flow-distributing plate, a cylinder body, a housing, a tilting tray and a transmission shaft, wherein a front end cover is connected with the housing through a bolt; a rear end cover is connected with the housing through a bolt; the cylinder body is in sliding fit to the housing through a self-lubricating guide post and a guide sleeve; a cylindrical spiral spring is mounted in a housing lug boss, and acts on the surface of a cylinder body lug boss, so that flow-distributing pair compression is realized; a universal rolling ball spring plunger is mounted on the base of a tilting tray lug boss, and a ball head of the universal rolling ball spring plunger acts on the surface of a pressure disc, so that sliding boot pair compression is realized. According to the complete-discharge compression type axial plunger pump or the motor provided by the invention, a sliding boot pair and a flow-distributing pair are in a discharge compression mode, and do not interfere each other, and an acting force arm of spring force is great; a sliding boot and the cylinder body are strong in anti-overturning capacity, and the spring is alwaysin a compression state, so that fatigue loss is relieved, and design requirements are reduced. The complete-discharge compression type axial plunger pump or motor is simple and practical in structure, is easy to assemble, and has a very good popularization value.