The utility model discloses a pre -assembling line cable tube, including protection pipe fitting and shroud ring, the protection pipe fitting includes body and body connection piece, and the locking bolt is installed to the equal fixedly connected with body connection piece in both ends of body in the through -hole of body connection piece, and the locking bolt is connect protection pipe fitting and shroud ring in proper order, and the shroud ring lies in the outside of body connection piece including the hoop body and hoop body coupling piece, hoop body coupling piece, and hoop body couplingpiece is through locking bolted connection body connection piece, this pre -assembling line cable tube, including protection pipe fitting and shroud ring, the shroud ring is installed by the department through the joint at two protection pipe fittings, and the shroud ring passes through locking bolted connection together, need steel pipe protection because of the road construction like buried cable, dig out the back with the cable, with two semicircular protect pipe fittings with the cable for the grasping bolt -up can accomplish the protection, need inadequately to extend like length, available shroud ring gets up multiple protection pipe connections, makes the construction installation become simple, not only saves time but also laborsaving.