The application of cellulose aerogel is restricted by its weak mechanical property and dimensional stability due to the hydrophilic effect of the hydroxyl groups on the molecular chains, which are prone to structural crumpling during solvent exchange and drying processes. In this paper, down feather fibers (DFF) was dispersed into hydroxyethyl cellulose (HEC) matrix to prepare DFF reinforced cellulose composite aerogel anticipating to improve the mechanical and insulating properties. The basic physical and mechanical properties of HEC/DFF composite aerogels were characterized. And their acoustic and thermal insulation properties were also investigated. The results showed that HEC/DFF composite aerogels had low density (0.045 ~ 0.080 g/cm 3 ) and high porosity (90.09% ~ 94.42%). The mechanical properties of HEC/DFF were obviously improved by increasing the compressive stresses at the 80% compressive strain about 135%, and the compression modulus increased from 46.37 kPa of pure HEC aerogel to 128.65 kPa. The reinforcement of DFF for HEC aerogels was arisen from the combination of physical and chemical strengthening action. HEC/DFF composite aerogel has sound absorption coefficient of 0.938, and the thermal conductivity of 0.06773 W/m·K, showing excellent sound absorption and good heat insulation properties. Therefore, this study provides a new method to reinforce cellulose composite aerogels with excellent insulation properties by using bio-based down feather fibers.