The work aims to prepare biodegradable waste paper/PETG wood-plastic composites modified by coupling agent and test their properties. The coupling agents KH550, KH560 and KH570 were used to modify the waste paper powder, and then the wood-plastic biocomposite were prepared with PETG. The effects of the addition of coupling agent on the structure, mechanical properties, water absorption, microstructure and thermal stability were studied by Fourier transform infrared spectroscopy, mechanical property detection, water absorption analysis, scanning electron microscopy and thermogravimetric analysis. KH550 had the best enhancement effect on the properties of the composites. When the mass fraction of KH550 was 1%, the tensile strength and flexural strength of the composites reached their peak values, increased by 32.8% and 13.7%, respectively. The coupling agent can significantly improve the mechanical properties and thermal stability of the composite and reduce its water absorption, so it has a good application prospect in the packaging field.