The work aims to prepare biodegradable cassava residues and PBS composites by compounding cassava residues and PBS to promote the recycling and reusing properties of cassava residues and replace plastics with cassava residues/PBS composites. Cassava residues and PBS were used to prepare the biodegradable composites. The effects of particle size and amount of biomass materials on the apparent structure, microstructure and mechanical properties of the composites were respectively studied by Fourier transform infrared spectroscopy, mechanical property detection, scanning electron microscopy and thermogravimetric analysis. The tensile strength and bending strength of the composites prepared under the hot pressing pressure of 10 MPa reached the peak of 16.96 MPa and 32.53 MPa respectively. Compared with the values under the hot pressing pressure of 4 MPa, the tensile strength and bending strength of the composites were increased by 69.77% and 148.7% respectively. Certain amount of cassava residues will not affect the comprehensive properties of materials under appropriate conditions, but can greatly improve the biodegradability of cassava residues/PBS composites. Therefore, cassava residues/PBS composite realizes the recycling of agricultural waste resources, improves the added value of crops, reduces the production cost of composite materials, and promotes the industrialization of biodegradable composite materials, which has broad development prospects in the field of biodegradable packaging.