The invention discloses a cable sheath vacuum pumping device. The cable sheath vacuum pumping device comprises a cable sheath. A cavity is formed in the cable sheath. The two sidewalls of the cable sheath are each provided with a first round port. Two communicating pipes are inserted into the two first round ports. The ends, far from the cable sheath, of the two communicating pipes are both provided with second round ports. Two rubber blocks are inserted in the two second round ports. The sides, far from the corresponding communicating pipes of the two rubber blocks are both fixedly connectedwith fixed plates. Each fixed plate is provided with a plurality of pay-off holes. Multiple cables are arranged between the two fixed plates. The ends, far from the fixed plates, of all the cables pass through the corresponding pay-off holes and penetrate through the communicating pipes, the rubber blocks and the sidewalls of the cable sheath to extent into the cavity. The cable sheath vacuum pumping device protects outer conductors of the cables by removing acid gas between the cable sheath and the cables when the cable sheath cools and shrinks, and the indexes of the cables are guaranteed. The cable sheath vacuum pumping device is simple in structure, convenient to use and practical.