Composite film-forming agent, waterproof liquid band-aid and preparation method of waterproof liquid band-aid

The invention provides a composite film-forming agent, a waterproof liquid band-aid and a preparation method of the waterproof liquid band-aid. The composite film-forming agent comprises polyvinyl acetal, nitrocellulose and tannic acid in a mass ratio of 1: (0.5-2): (0.01-0.1), dissolving polyvinyl acetal and the nitrocellulose in a mixed solvent of acetone/ethanol, then adding tannic acid, reacting for 5-20 hours, then adding water to precipitate, and then washing and drying to obtain the three-component composite film-forming agent. The composite film-forming agent is used for the band-aid, the plasticizer, the analgesic, the antibacterial agent and other components are added, and the composite film-forming agent is rich in hydrogen bonds, so that when the band-aid is used, the toughness, the waterproofness and the air permeability of a formed film are remarkably improved, the film is not prone to chap and damage in the using process, is not prone to wound infection caused by water permeation and is easy to