As an environmentally-friendly and cost-effective biological 3D carbon nanomaterial, bacterial cellulose (BC) has been gradually used in flexible electronics. However, the application of BC in electrochemical CO2 reduction (ECR-CO2) reactions is rare. Herein, to promote its applications in ECR-CO2, BC with a 3D network structure was used as a catalyst carrier, and a catalyst electrode (CuO/Cu@BC) supporting Cu and CuO nanocomposites was prepared by in situ chemical reduction. To investigate optimal conditions, the soaking time of the BC membrane was changed to achieve structure regulation. The results revealed that at a soaking time of 24 h, the CuO/Cu24h@BC electrode exhibited a high electroactive area (12 mF/cm2), providing a considerable increase in the number of active sites for CO2 absorption; this result was verified by investigation of the electrocatalytic activity and performance. The electrochemical impedance test revealed that the activation resistor of the electrode was small and that the activation energy was high, thereby improving the electron conductivity by building an efficient transfer highway for Cu and CuO. Scanning electron microscopy analysis of the morphology of the CuO/Cu@BC electrode revealed a uniform coverage in addition to the even decoration of nanoparticles (50~70 nm) on the top, facilitating the penetration of the electrolyte. On the other hand, the seaweed structure of the CuO/Cu8h@BC electrode and the adverse combination of the nanoparticles of the CuO/Cu16h@BC electrode were disadvantageous to the transformation of CO2. In terms of the product analysis by ECR-CO2, the CuO/Cu24h@BC electrode exhibited outstanding selectivity for CO with a faradaic efficiency of 52% at a potential of ?0.6 V vs. RHE in a 0.5 mol/L KHCO3 electrolyte. All the above results demonstrated that BC was superior as an efficient electrode substrate to support electrocatalysts for CO2 reduction and that the CuO/Cu24h@BC electrode exhibited good performance for the reduction of CO2 to CO.