In order to improve the shrinkage resistance of wool fabrics, a new method that combine ionic liquid and chitosan was researched in this paper. Wool fabric was first pretreated with 1 - butyl - 3 - methyl bromination imidazole([Bmim]Br）, and subsequently was treated with chitosan. Pretreatment temperature and time, and chitosan concentration of post-treatment were studied in this paper. Results showed that wool fabrics treated with [Bmim]Br at 80°C for 2 hours and post-treated in 1.0% chitosan acetic acid solution exhibit good shrinkage resistance. In addition, SEM images of ionic liquid treated wool fiber indicates that the scales have been destroyed, and the surface is covered with a layer of film after post-treated with chitosan.