The invention relates to a reciprocating screw vacuum compressor. The compressor is characterized in that a driven wheel is provided with a reciprocating screw transmission mechanism formed by a driven wheel supporting shaft, a gear transmitting and reversing system, hollow shafts, bearing blocks, hollow screw rods, nuts, nut sleeves, connecting sleeves, reversing rods, a spring mechanism and a jaw clutch; tandem piston units in a vacuum compression device formed by cylinders, pistons, sealing connecting pipes, sealing elements A, intermediate separate cavities, sealing elements B, a front separate cavity, a rear separate cavity, three-way intake valves, three-way exhaust valves, intermediate three-way exhaust valves, intermediate three-way intake valves, a main exhaust pipe and a main intake pipe are driven by reversion of the reversing rods in the reciprocating screw transmission mechanism to continuously reciprocate in the cylinders, thus realizing the vacuumizing and compressing functions of the vacuum compressor. The vacuum compressor not only has reasonable design and compact structure, but also has the advantages of energy conservation, no vibration, no noises, conformity with the environmental protection requirement, stable operation, convenience in operation and use and the like.