The invention discloses a method for preparing xylooligosaccharide by utilizing viscose fiber to squeeze waste alkaline liquor and belongs to the technical field of biochemical engineering. By adoption of the method, the problem of waste liquor treatment in a viscose fiber plant can be solved, and the environment can be protected. The method comprises the following steps of based on squeezed waste alkaline liquor in the viscose fiber plant as materials, firstly carrying out ultrafiltration-membrane separation, reusing permeated liquor, carrying out neutralization on concentrated liquor, carrying out enzymolysis with xylan, decoloring with active carbon, desalting with ion exchange resin, freezing, drying and finally preparing the xylooligosaccharide. The method disclosed by the invention has the advantages that the hemicellulose in the waste alkaline liquor is squeezed by utilizing the viscose fiber, and the alkaline liquor is also recovered, so that the resources are saved and the utilization of wastes is also realized.