Abstract: Thermoplastic starch (TPS) prepared from natural starch has complete biodegradability and thermoplastic processability similar to traditional plastics, but its poor mechanical properties and water resistance limit its development. Biodegradable polyvinyl alcohol fiber (PVAF) was grafted onto its surface with glycyl methacrylate (GMA) containing epoxy and vinyl groups. In the process of twin-screw extrusion, the hydroxyl group on starch macromolecule reacted with the epoxy group of PVAF surface grafted with GMA (GMA-PVAF) to form a crosslinked structure, thus improving the mechanical properties of thermoplastic starch plastics. The results shows that GMA-PVAF shows obvious coating, which has the characteristic infrared absorption peaks of ester carbonyl group and epoxy group in GMA. The crystallinity decreases significantly, and the glass transition temperature (T_g) increases from 95.8℃ to 100.7℃. Thermogravimetric analysis shows that the mass fraction of coating is about 8.77wt%. When the content of GMA-PVAF is 1.5wt%, the tensile strength of GMA-PVAF/TPS composite increases from 3.00 MPa to 4.99 MPa, the elongation at break is 146.84%, the bending strength increases from 1.82 MPa to 11.62 MPa, and the mechanical properties are significantly improved.