The inventive embodiments disclose an apparatus and method for installing a 220 kV line arrester in a live working state. The apparatus comprises: a hanging ladder that is connected to one end of a top cross-arm of an electric-tower by a first insulated lifting rope; a pulley block that is fixed below the top cross-arm of the electric-tower by a second insulated lifting rope, wherein the other end of the pulley block is connected to the hanging ladder; a third insulated lifting rope that is fixed at the top cross-arm of the electric-tower, wherein the other end of the third insulated lifting rope hangs in the air. Thus, during live working, an operating person huddles up and sits in the hanging ladder, and then utilizes the pulley block to transport the hanging ladder to an operation position. Since the hanging ladder is an equipotential object and creates an equipotential space in order to protect the operating personal during the course of the transportation, the inventive apparatus and method can implement the live installation of the 220 kV line arrester in a easier and faster way, save both time and labor, address a problem of an apparatus for installing a 220 kV line arrester in a live working state that currently is not yet mature in the existing art, and have guiding significance for live working of double-circuit lines with 220 kV or more than 220 kV.