The film-forming aids of water-based coatings are also called coagulants, coalescing agents, film-forming co-solvents or co-solvents, which can dissolve and swell polymer particles in the emulsion, so that the particles can also follow the Volatilization produces plastic flow and elastic deformation to agglomerate into a film, but it can volatilize and escape in a short time after film formation without affecting the glass transition temperature of the coating film. The coating film does not stick back at high temperatures. Film-forming aids are high-boiling organic solvents with a high dissolving power of several hundred molecular weights, mostly alcohols, alcohol esters, and alcohol-ether compounds. In fact, film-forming aids are a solvent for polymers. During the drying process, the remaining film-forming aid after the water volatilizes the polymer droplets and fuses into a continuous film. In addition to the dissolving effect, the film-forming aid will also temporarily plasticize the polymer and form a film. Auxiliary agent is a kind of volatile temporary plasticizer, which can promote the plastic flow and elastic deformation of latex particles, improve its coalescence, and form a film in a wide range of application temperature.