A method for vertically grounding and leading down form an outer side of a composite pole tower and pole tower thereof, wherein the method includes the following steps: extending an upper metal cross arm from an extended line of at least one side of a ground wire cross arm, vertically leading down a ground down-leading wire from a distal end of the upper metal cross arm, connecting the ground down-leading wire to the pole tower via a lower metal cross arm at a distance under a lower lead, and grounding the ground down-leading wire along a tower body of the pole tower, wherein when an lower portion of the tower body is a metal pipe, the ground down-leading wire is selectively directly connected to the metal pipe via the lower metal cross arm. The method facilitates in compressing the width of the transmission corridor to a maximum extent as well as designing a lightning protection, preventing the ground down-leading wire from short-circuiting with the tower body, and realizing the insulation function of the composite material tower body. The manner of using unilateral ground down-leading wire saves material, and is economical and simple in structure.