Abstract: A water-borne resin composition for polyolefin is obtained by graft polymerizing polypropylene chloride resin having a chlorine degree of about 10-40% and an acryl monomer. First, polypropylene chloride resin solution is prepared by mixing about 5-30 parts by weight of polypropylene chloride resin having a chlorine degree of about 10-40 and about 5-30 parts by weight of a hydrophilic solvent. Then, an acryl monomer solution is prepared by mixing about 70-95 parts by weight of an acryl monomer, a solvent and an initiator. The acryl monomer solution is dropped into the polypropylene resin solution at a temperature of about 80-130° C. and thus obtained product is neutralized and diluted. The composition has a good adhesiveness onto polyolefin, so that the composition may be applied as a water-borne paint composition for polyolefin-based substrate.