The utility model relates to a combined pre-built-in bolt casing tube used in a non-broken piece orbit, which belongs to the technical field of railway construction. The utility model is provided with a nylon bolt casing tube, wherein a metal casing tube is sheathed outside the nylon bolt casing tube, screw threads matched with each other are arranged on the inner wall of the metal casing tube and the outer wall of the bolt casing tube, and the metal casing tube is sheathed on the nylon bolt casing tube by the screw threads. The utility model has the advantages that the nylon casing tube can be conveniently replaced, and concrete sleeper and road bed are not damaged; the utility model can improve the stress condition of the nylon casing tube, and the damage, such as cracking, breakage, etc., is reduced. The utility model can be used for replacing the existing nylon bolt casing tube.