A method for preparing a composite brush plated deformation line diamond wire saw, comprising the following steps of: preparing materials, selecting diamond or surface metallized diamond and nonconductive free particles, ultrasonically washing, using distilled water to repeatedly wash and bake; taking a straight line metal wire with the diameter of 0.1-2 mm as a cathode and an electric brush plating pen as an anode, washing the metal wire, pre-brush plating the metal wire, and then washing with deionized water; electric brush plating an amorphous state plating layer, taking pre-brushed platedmetal wire as a cathode and the electric brush plating pen as the anode, and electric brush plating the amorphous state plating layer to obtain the diamond wire saw; and deforming the diamond wire saw through a deformer, thermally processing to obtain a latter deformation line diamond wire saw. The preparation technology has a simple device, high production efficiency, and recycle use of plating solution; and the produced wire saw has few shortcoming, a good performance and a long service life.