The invention discloses a power transmission line tower single-phase grounding device. A plurality of mutually-meshed gears are arranged in a casing. A main drive gear is connected with a crank through a shaft. A last driven gear is connected with a ratchet through a shaft. A pawl hinged to a connection rod is inserted in teeth of the ratchet. The connection rod is fixedly connected to the casing. The other end of ratchet is connected with a connection plate. The connection plate is hinged to a support plate at one end of a grounding wire box. The other end of the grounding wire box is connected with a protection pipe. One end of a grounding copper rod passes through the protection pipe and is connected with a grounding wire in the grounding wire box. The other end of the grounding copper rod is connected with a rotary connection plate. The protection pipe is provided with a spacing hole at an adaptive position. A handle passing through the spacing hole is fixedly connected with the grounding copper rod. The invention solves problems in the prior art that as the operator climbs a tower up and down with the load, the grounding wire hanging is time-consuming and labor-consuming, the operation efficiency is improved, the operation risk is lowered, the installation is simple, the cost is low, and the popularization and usage in the power transmission and production field are extremely easy.