The invention discloses a single-loop on-off steel tube pole tower adopting a triangular cross beam. The single-loop on-off steel tube pole tower comprises a tower body, a top-layer ground wire cross beam, an upper-layer guide wire cross beam, a middle-layer guide wire cross beam and a lower-layer guide wire cross beam, wherein the top-layer ground wire cross beam, from the tower body and back to an on-off side, is provided with a cross beam with one side perpendicular to a target on-off line, and is provided with a one-sided triangular cross beam towards the on-off side; the upper-layer guide wire cross beam is provided with a one-sided triangular cross beam from the tower body and towards the on-off side; the middle-layer guide wire cross beam is provided with a two-sided cross beam from the tower body and parallel to the target on-off line direction, and, from the tower body and back to the on-off side, is provided with a one-sided cross beam towards the on-off side. The single-loop on-off steel tube pole tower adopting a triangular cross beam only adopts a base pole tower to realize the single-loop on-off, and reduce the quantity of newly-built pole towers; after the line is shut on and shut off, double loops are formed to continuously arrange the line, thereby avoiding the use of a double-loop branch rod, not changing a guide wire arrangement mode of adjacent pole towers and reducing the possibility of modifying adjacent towers.