Abstract: The self-emulsifying miniemulsion of polyurethane prepolymer with terminal groups of isocyanate (-NCO) was prepared using polytetrahydrofuran glycol,polyethylene glycol adipate,isophorone diisocyanate,non-ionic hydrophilic monomers of MO3 and liquid paraffin.The content of -NCO groups in miniemulsion was determined by modified acetone/toluene-dibutylamine titration method,and the structure of hydrolysate in self-emulsifying was characterized by FTIR.The model of hydrolysis reaction of -NCO groups was also established based on some assumptions,and was fitted under the conditions of different temperatures and different amounts of MO3.The results show that the hydrolysate was poly(urea-urethane).The fitting results fitted well with the physical model,in self-emulsifying miniemulsion,the apparent activation energy of hydrolysis reaction of -NCO groups was 60.2 kJ·mol-1,and the hydrolysis reaction rate was accelerated by the increase of the content of hydrophilic chain segment.