The invention relates to an energy-saving compact vacuum extruder, which comprises speed reducer (1), aerated clutch (2), block coupler (3), extruding axle (19), transmission gears (5, 6, 15), mixing axles (4, 26), Haf mixing blade (8), vacuum room (11), compressing plate (12), extruding cylinder (13), head (14), extruding mold (21), upper, middle, and lower boxes (22, 23, 25), machine base (24), and material hopper (7). The invention is characterized in that: the output axle wheel (17) of power machine (18) via transmission belt (16) drives the aerated clutch belt wheel (2) at the input of speed reducer (1); the output of speed reducer via block coupler (3) rotates the extruding axle (19); the active gear (15) at the back extruding axle makes the inactive gear (5) to rotate the active mixing axle (4), and makes the gear (6) axial with active gear (15) to rotate the inactive mixing axle (26). The invention can reduce mechanical friction and save enegy.