The invention discloses a triangular brace for hot-line work and a use method. The disadvantage that the existing wire support tool can only make line spacing adjusting on two cables is solved. The triangular brace comprises multiple groups of support groups for strutting a first cable, a second cable and a third cable; each support group comprises a support rod A, a support rod B and a positioning rod between the first cable and the second cable; one end of the support rod B is supported on the third cable, and the other end of the support rod B is rotatably connected to the brace A; one endof the positioning rod is hinged on a support rod through a rotatable device, and the other end of the positioning rod is fastened on the other support rod through the fixing device. The triangular brace disclosed by the invention has the advantage of changing the line spacing among three cables of three electric cables, the positioning rod is flexible so as to facilitate the adjusting of the worker.