The invention relates to a preparing method for self-healing polysaccharide hydrogel. The preparing method comprises the steps that cellulose is added into ionic liquid to be dissolved, the mixture is then cooled to the room temperature, and a cellulose solution is obtained; the cellulose solution is heated and dripped with tert-butyl acetoacetate under the protection condition of introducing nitrogen, a reaction is carried out at the constant temperature, the solution is then cooled to the room temperature, purified and subjected to vacuum drying, and acetoacetic acid cellulose is obtained; under the room temperature, a chitosan solution is added into the acetoacetic acid cellulose solution, oscillated and mixed, and the self-healing polysaccharide hydrogel is obtained. The polysaccharide hydrogel prepared through the method has the self-healing performance, and has the pH responsiveness at the same time. The preparing method is simple in process, rich in raw material and suitable for modification of most polysaccharide derivatives; meanwhile, due to the good biocompatibility of cellulose and chitosan, the prepared polysaccharide hydrogel has good application prospects in the fields such as tissue engineering repair, medicine controlled release and biological bionics.