The work aims to develop new biodegradable composite materials to alleviate environmental pollution caused by traditional petroleum-based materials. With high density polyethylene (HDPE) as substrate and thermoplastic starch (TPS) as modifier and additive, the composite sheet with TPS content of 0, 10%, 20%, 30% and 40% was prepared by melt blending. The influence of TPS content on the physical properties of TPS/HDPE sheet was analyzed and compared. It was found that the addition of TPS reduced the toughness and plasticity and increased the rigidity of the material. When TPS content reached 40%, the tensile strength decreased by 52.3% compared with HDPE, and the elongation at break decreased by over 90%, while the bending strength and bending modulus increased by 100.2% and 70.5% respectively. Infrared spectral analysis showed that a new peak was found at 1200 cm-1. DSC analysis showed that the melting temperature of the material decreased from 136.1 ℃ to 132.7 ℃. When the content of TPS was 40%, the hydrophobicity of composites was the best. The study shows that the addition of certain amount of TPS could improve the rigidity and hydrophobicity of HDPE. It provides certain theoretical basis for preparation of high-performance starch-based food contact materials.