In order to meet the hardness requirements of the film on the polyethylene terephthalate（PET） substrate and avoid adding amine neutralizing agents，a modified sulfonated waterborne polyurethane（SWPU）emulsion，which could be cured by UV light/heat due to the introduced double bonds and epoxy groups，was synthesized from diisocyanate，sulfonate polyols and so on. The structure of SWPU emulsion was characterized by infrared spectroscopy（FT-IR）. The effects of R values（molar ratio of isocyanate groups to hydroxyl groups） and sulfonate polyols dosage on the particle size of SWPU emulsions，mechanical properties，water contact angle，water absorption，thermal stability and other properties of coating were investigated. The results showed that with the increase of R value，the particle size of emulsion and the hardness of the coating gradually increased. When R value was 1. 6， the coating exhibited high hardness and the performance of emulsion was relatively stable. Inaddition，the particle size of the emulsion gradually decreased with the increase of sulfonatepolyols dosage. When the sulfonate polyols dosage was 6%，the hardness of coating reached 3H，the flexibility was 1 mm，the adhesion was grade 0，the water contact angle of coating was 68. 2°，and the water absorption was 8. 85%. Meanwhile，the film also indicated goodmechanical properties and thermal stability. The modified sulfonated waterborne polyurethanecoatings could meet the requirements of the target application.