The invention discloses a preparation method for a cellulose / chitosan composite modified degradable antibacterial membrane, belonging to the technical field of preparation of antibacterial membranes. The preparation method comprises the following steps: with wheat straw and shrimp shell as raw materials, subjecting the wheat straw to cleaning, solarization and crushing, adding a sodium hydroxide solution, cooking the crushed wheat straw with the sodium hydroxide solution, then subjecting the cooked wheat straw and cellulose hydrolase to an enzymatic hydrolysis reaction, adding sulfuric acid and hydrochloric acid into a reaction vessel, carrying out heating and hydrolysis and then successively carrying out ultrasonic treatment, filtering, drying and crushing so as to obtain modified cellulose; and subjecting the shrimp shells to cleaning, drying and milling into powder, soaking the obtained shrimp shell powder with hydrochloric acid, adding liquid alkali and carrying out water-bath heating, then carrying out pumping filtration so as to obtain a filter cake, drying and crushing the filter cake, adding a mixed solution of modified cellulose and glacial acetate acid, then carrying out ultrasonic treatment and ultraviolet lamp sterilization and finally, forming the membrane in a membrane forming machine. The invention has the following beneficial effects: the degradable antibacterial membrane is prepared through compounding and modification of the wheat straw and shrimp shells, so waste of resources is prevented; and the prepared degradable antibacterial membrane is safe, environment-friendly, naturally degradable and pollution-free to the environment.