The invention provides a synthetic method of an environment-friendly water-based resin adhesive applied to high-density polyethylene fiber. The synthetic method disclosed by the invention has a following technical scheme: two kinds of polyalcohols, toluene diisocynate and hexamethylene diisocyanate are utilized as monomers, tackifying resin is added, and polymer is prepared by prepolymerization, neutralization, emulsification and chain extension. The tackifying resin in a structure of a polyurethane adhesive, prepared by the method can improve wettability and initial adhesiveness of the adhesive to a base material, and furthermore, peel strength and water resistance of a solidified adhered position are improved.