The invention belongs to the technical field of functional food engineering and particularly relates to a preparation method of truffle polysaccharide. The preparation method is characterized by comprising the following steps: preparing truffle polysaccharide extract, preparing truffle polysaccharide concentrate, drying the truffle polysaccharide concentrate, vacuum packaging truffle polysaccharide powder, then transporting or storing and the like. According to the method, the truffle polysaccharide is extracted mainly by utilizing water as a solvent, the truffle polysaccharide extract is concentrated by membrane separation equipment and the truffle polysaccharide powder is prepared via a spray drying process. The method is simple to operate, and the prepared truffle polysaccharide is high in activity, long in storage time and convenient to transport, store and utilize.