The invention discloses a harness tube fixing device which comprises a main body and a first fixing structure. The main body comprises a cuboid, the middle of the top of the cuboid is provided with across through hole, and the inner sides of two opposite edges in the cross through hole in the transverse length direction of the cuboid are provided with limiting check blocks. The first fixing structure includes a supporting rod. A first arc-shaped limiting member and a second arc-shaped limiting member are symmetrically arranged on both sides of the top of the supporting rod. Evenly-distributedbarb structures are disposed on the two sides of the bottom of the supporting rod. The bottom of the supporting rod is disposed in the cross through hole of the cuboid in a pluggable mode, and the limiting check blocks and the barb structures are clamped. According to the harness tube fixing device, when two harness tubes are fixed, the two harness tubes are separated through the supporting rod and are not in contact with each other. Besides, the insertion depth of the supporting rod in the cuboid is adjustable, the fixation of the harness tubes of different thicknesses can be achieved, and the universality is high.