The present invention discloses a method for extracting xylooligosaccharide from water hyacinth. The method comprises pre-treating water hyacinth and extracting xylooligosaccharide. The method has the following advantages that: the water hyacinth resource is completely utilized, the waste is changed into treasure, and the problem of environment pollution caused by excessive water hyacinth is solved. In addition, the method has characteristics of simple preparation process and easy operation, and is easily subjected to industrial production, and the xylooligosaccharide extraction yield is high and is up to 7.8%.