Sound absorbing materials are widely used in the field of automotive industry. Biomass materials are abundant in nature, and some biomass has natural sound absorption and noise reduction properties. Biomass sound absorption material is green and pollution-free, and has obvious noise reduction effect on middle and high frequency noise, large specific surface area, light weight, and strong sound absorption effect. In order to analyze the sound absorption and physical properties of biomass sound absorbing materials, the noise reduction performance of the different structure of biomass sound absorbing materials were analyzed. In this paper, the biomass sound absorbing materials coconut fiber and coconut shell activated carbon particles were used to make samples. Coconut shell activated carbon sound absorption material (CSAC) was made. The cylindrical holes was made and filled with coconut fiber materials to form composite sound absorbing materials (CSAC-F). The acoustic performance of impedance tube was tested based on the acoustic absorption coefficient, and the physical performance was studied by means of Scanning Electron Microscope (SEM), Brunauer, Emmett and Teller (BET), X-ray diffraction (XRD), Fourier Transform Infrared Spectrometer (FTIR), Thermogravimetric (TGA) and other detection methods. In contrast, the sound absorption effect of CSAC-F was better in the middle and low frequency range. The microstructure of the material was analyzed and the mechanism of noise reduction was studied. This research will provide a new way for the research and development of sound absorbing materials in the automotive industry, and biomass sound absorbing materials have potential applications in the noise absorption and vibration control of automotive interior.