The invention discloses a main shell supporting and lubrication structure of a combined hydraulic pump motor. The main shell supporting and lubrication structure comprises a shell, wherein one end face of the shell is set as an mounting surface (1) matched with an object part, and the other opposite end face of the shell is set as a rear cover fitting surface (7); a hydraulic motor shaft passing hole (2) and a hydraulic pump shaft passing hole (3) are formed in the mounting surface (1) matched with the object part, and a bearing hole is formed in the rear cover fitting surface (7); a motor side view window (4), a servo operating valve group mounting hole (5), a pump side view window and a pump swash plate mounting hole (6) are formed in the circumferential side face of the shell. The main shell supporting and lubrication structure adopts a scheme of parallel arrangement of a pump shaft and a motor shaft and adopts the aluminum shell, and the design is compact. Moreover, a concept of envelope design is adopted, an oil filling way, a lubricating oil way and a return oil way are integrated into the shell. Therefore, the lightweight design is realized, and the integration level and the power density are improved.