The invention relates to a preparation method of an electroplating diamond fret saw, comprising the following technological processes: 1. roughening processing is carried out to micrometer diamond particles in advance, nanometer diamond powder is added in cationic surface active agents according to the proportion of 1 : 3 by mass ratio, so as to prepare uniform and stable nanometer diamond powder suspending liquid, plating solution is arranged in an electroplating tank, after the weighted nanometer diamond powder suspending liquid is mixed with the micrometer diamond particles according to the proportion of 1 : 3 by mass ratio, and then the mixture is added in the plating solution, the plating solution is circulated continuously, and nickel aminosulfonate is main material in the plating liquid, and boracic acid and nickel chloride are additionally added, and a magnetic stirring device is arranged in the electroplating tank; 2. a steel wire continuously and uniformly passes through the electroplating tank, under the action of electrical current, nickel ions move to cathode from anode, so as to drive the nanometer diamond powder and the micrometer diamond particles to move to the steel wire, so as to lead the steel wire to be plated with the nanometer diamond powder and the micrometer diamond particles, meanwhile, chemical nickel-plating is carried out to the steel wire; 3. after the steel wire is separated from the electroplating tank, wires are wound up after being cleaned and dried. The method can continuously and quickly produce electroplating diamond fret saw, and the production efficiency is high.