Polymer-based damping materials are widely used in various industrial fields due to their excellent vibration reduction performance. With the enhancement of environmental awareness, the preparation of high-performance damping composites using green renewable resources is of great significance for the sustainable development of this field. In this study, coffee grounds modified polyurethane-based damping composites were prepared by two-step method. The effects of coffee grounds content and particle size on damping properties, thermal stability, tensile strength and elongation at break were studied by means of DMA、TGA and universal mechanical testing machine. The results show that the damping and mechanical properties and thermal stability of the composite can be effectively improved by adding appropriate amount of coffee grounds. When the mass fraction of coffee grounds is 10 %, the damping effect of the composite is best, the loss factor is up to 0.66, the tensile strength increases by 33.8%, and the elongation at break increases by 12.9%.