Abstract: Two-component waterborne polyurethane coating consists of a polyisocyanate as a curing agent and a dispersion polyol of aqueous crosslinked polyurethane, which was synthesized by using polycarbonate diol(PCDL), dimethylol propionic acid(DMPA) and isophorone diisocyanate(IPDI) as preplolymerization material and then extended with trimethylol propane(TMP). It was applied on cotton fabrics surface in order to research the effect of polyurethane coating on cotton fabrics water resistance, the treated cotton fabrics was characterized with scanning electron microscopy(SEM), contact angle and water absorption analysis. The results indicate that the fiber bundles of treated cotton fabrics surface is tightly conglutinated together, it shows very good hydrophobicity, the contact angles for water can reach 130°, and the water absorption of treated cotton fabrics decrease to 9%. In addition, it also shows good washing durability, the contact angles still reach 90° even after 12 washing cycles and the water absorption is much smaller.