The invention relates to a preparation method for an antibacterial liquid-absorbing gauze, which belongs to the field of preparation of medical dressings. According to the invention, a quaternary ammonium salt group is introduced onto a cellulose molecular chain of a degreased gauze through an epoxide ring-opening or nucleophilic substitution reaction, so polycation characteristics of cellulose of the gauze are increased, and antibacterial properties of the gauze are improved; through controlling of a mol ratio of a hydroxyl group to a quaternary ammonium salt on the cellulose molecular chain of the degreased gauze and reaction conditions, the degree of substitution of the quaternary ammonium salt on the cellulose molecular chain is in a range of 5 to 80%, so the reacted gauze has high antibacterial properties and high liquid absorption performance and can maintain the basic form of yarns after absorption of liquid. The antibacterial liquid-absorbing gauze prepared by using the preparation method provided by the invention overcomes the defect of a single function of a conventional medical gauze, is applicable to an infectious wound with a great amount of exudate or an infectible wound and exerts the effects of killing of bacteria on the surface of the wound and absorption of exudate on the surface of the wound. The preparation method for the antibacterial liquid-absorbing gauze has the advantages of easiness, low cost and easy industrial production.