In this study, a series of aqueous polyurethane modified by poly(dimethyl siloxane) PDMS were synthesized, which were based on polyoxytetramethylene glycol (PTMG), isophorone diisocyanate (IPDI), dimethylol propionic acid (DMPA), and PDMS. The copolymer was characterized by FTIR and the fraction of hydrogen bonded carbonyl group was determined through decomposition of C=O stretching. Energy dispersive X-ray analyzer (EDX) was used to investigate the siloxane concentration on the surface and bulk regions. The morphology of aqueous polyurethane before and after modification was studied by SAXS, including the interface between soft and hard micro-domain, the size and shape of the dispersive particles, as well as the degree of the phase separation. Influence on the morphology structure of aqueous polyurethane in different type and content of organic silicone was studied. It was shown that the degree of hydrogen bonding and phase separation of aqueous polyurethane decreased after the introduction the PDMS resulted from the migration of PDMS to the surface of the film. Therefore, water resistance improved a lot after the introduction of PDMS with different structures, and the tensile strength and elongation of APDMS(PDMS terminated by hydroxyalkyl) decreased while those of EPDMS(PDMS terminated by hydroxyl polyether) appeared little increase at low content and than decreased. (C) 2007 Wiley Periodicals, Inc.