A method for preparing a high-efficiency antibacterial quaternary ammonium salt chitosan composite gel coating layer is provided; by using solutions of chitosan and polyvinyl alcohol, the gel coating layer having hydrophilic surface and being stable in an aqueous environment is obtained by physical coating; the material is endowed with an antibacterial function by quaternary ammonium salinization treatment, and the hydrophilicity of the material is improved by the polyvinyl alcohol component; the coating layer has good gram positive and gram negative bacteria adhesion resistant and sterilization abilities. The method is simple and fast in process, moderate in conditions, easy to implement by spin coating, dip coating, spray coating and other methods which can be implemented industrially, wide in application range, and capable of effectively improving the antibacterial properties, biocompatibility and lubrication of the surface of medical devices.