2-[(2-aminoethyl)amino]-ethanesulfonic acid monosodium salt (AAS) was selected as hydrophilic chain extender. By the introduction of hydrophilic group into CA molecular through IPDI, under the catalysis of DBTDL, a kind of sulfonate waterborne cellulose acetate emulsion (SWCA) was prepared, and cast into a film. The structure and properties of SWCA and coating film were characterized by FTIR, nano-particle size analyzer, viscometer, TEM, SEM, contact angle measuring instrument, XRD and TGA. The effects of IPDI and AAS molar ratio on particle size, viscosity, surface morphology and water resistance of SWCA were investigated. The results demonstrated that when n(IPDI/AAS)=1.1, the emulsion was the most stable, and microscopic morphology was in oil-in-water (O/W) core-shell structure; the particle size and dispersion coefficient (PDI) of the emulsion were the smallest (128 nm and 0.112, respectively); Meanwhile, the apparent viscosity of the emulsion was 79.8 mP?s, and the resulting film was compact and smooth. When n(IPDI/AAS) ranged from 1.1 to 1.4, the film contact angle increased from (75.9??2?) to (110.2??2?) with the decrease of n(IPDI/AAS). In addition, microcrystalline or subcrystalline SWCA film was obtained after the modification. Compared with CA, the SWCA coating film has weaker crystallinity, and it has a microcrystalline or subcrystalline structure and has good heat resistance.