Abstract: A solvent-free adhesion-promoting chain extender, a preparation method therefor, and an application thereof are disclosed. The method includes the following steps: mixing an aromatic vinyl monomer, an acrylate-based monomer, an initiator, and water, then heating the mixture for polymerization, and subjecting the product to a secondary reaction by a twin-screen extruder for granulation, to prepare the extender. The obtained epoxy functionalized chain extender can be applied to a recycled material of a polyester structure and can be used for the repair and growth of molecular chains of biobased and biodegradable plastics of a polyester structure. The method features no use of a solvent in a process route, low investment, easily available apparatuses, low emission in the process route, and simple process control; in addition, the product has stable composition and is easy to use, and thus can be widely used, such as medical treatment, packaging, home appliances, automobiles, and aviation.