The invention discloses a method for synthesizing a high-weatherability red waterborne polyurethane emulsion, belonging to the field of the chemical industry. The method comprises the following steps:subjecting oligomeric diol, aliphatic diisocyanate, iron-rich red attapulgite and a hydrophilic chain extender to a stepwise polymerization reaction so as to synthesize a red attapulgite-modified hydrophilic polyurethane prepolymer; then subjecting the prepolymer to self-emulsification and dispersion in metered water; and then adding a small-molecule diamine chain extender for chain extension soas to obtain the red attapulgite-modified red waterborne polyurethane emulsion. The synthetic method of the invention is convenient to operate, energy-saving and environmentally friendly; the preparedred waterborne polyurethane emulsion has a solid content of more than 30 wt.% and a pH value in a range of 6.0-7.0; and a coating product of the emulsion has the advantages of good water resistance,high weather resistance, bright and beautiful colors, etc., and shows good market prospects.