The invention relates to a resin binder for a cold core box, especially to a polyurethane-based aromatic hydrocarbon-free resin binder for the cold core box. The polyurethane-based aromatic hydrocarbon-free resin binder comprises a component a containing phenolic resin and a component b containing polyisocyanate, wherein the component a and/or the component b contains one or more plant oil as a solvent. According to the invention, plant oil is low in price and easily available; when plant oil is used for replacing an aromatic hydrocarbon solvent, compounds of benzene, toluene, xylene, 1,2,4-trimethylbenzene and naphthalene and other aromatic compounds can be eliminated in preparation of the binder; so a binder system is free of volatile organic compounds and low in VOC content, formation of undesirable gas, smog and flavor can be reduced or eliminated in the processes of casting, cooling and sand stripping via vibration.