The invention relates to a preparation method of special coating resin composition for polyethylene. The preparation method comprises the following steps of: adding a peroxide crosslinking agent accounting for 0.001-0.5% of low-density polyethylene into the low-density polyethylene, and mixing and granulating to prepare the coating resin for the polyethylene, wherein the peroxide crosslinking agent consists of alkyl peroxide, lipid peroxide, diacyl peroxide and hydroperoxide, each of which accounts for 55-85%/5-15%/5-15%/5-15% according to the percentage by weight; the extrusion temperature of an extrusion machine is 150-250 DEG C, and the rotating speed of a screw is 20-60r/min; and the MFR (Melt Flow Rate) of the low-density polyethylene is 5.0-10.0g/10min, and the density is 0.915-0.925g/cm<3>. The special coating resin composition has the characteristics of high strength, good toughness, strong adhesive force and uniform filing forming and the like and is mainly used for surface coating, paper-plastic lamination, a bonding layer and film lamination of plastic woven bags.