The invention provides a method for finishing wool fabric by compositing chitosan/TiO2, which comprises the following steps: A)pretreating fabric; B)preparing composite finishing liquor, taking butyl titanate and dissolving in ethanol, adding diethanolamine, uniformly stirring and adding mixed liquor mixed by ethanol and water, heating, stirring under a backflow state to form nano TiO2 sol; adding chitosan, citric acid and sodium hypophosphate in the nano TiO2 sol, uniformly stirring to obtain the composite finishing liquor; C)finishing wool fabric, placing wool fabric in the composite finishing liquor, dipping and padding twice, wherein mangle expression is 85% and padding temperature is 50-65%; D)predrying; E)baking; F)washing; and G)drying. According to the finishing method, chitosan and nano TiO2 sol are employed as the composite finishing liquor, the finished wool fabric has good antibiosis, shrinkproof, ultraviolet resistance and anti-insolation performances; the finishing method generates no pollution on human body and environment, and the finished wool fabric has good hand feeling.