The invention aims at providing a preparation method of a water purifying material which has good electronic transmission performance, an even film layer and higher mechanical strength. Chitosan in the preparation method disclosed by the invention has the advantages of good adsorptive property, environmental friendliness, stable performance in preparing a composite material with titanium dioxide and graphene, ability in improving tensile property, tear resistance and adsorption performance of the composite material and convenience in recycling water purifying material.