CO₂ electroreduction has been regarded as an appealing strategy for renewable energy storage. Recently, bismuth (Bi) electrocatalysts have attracted much attention due to their excellent formate selectivity. However, many reported Bi electrocatalysts suffer from low current densities, which are insufficient for industrial applications. To reach the goal of high current CO₂ reduction to formate, we fabricate Bi nanosheets (NS) with high activity through edge/terrace control and defect engineering strategy. Bi NS with preferential exposure sites are obtained by topotactic transformation, and the processes are clearly monitored by in-situ Raman and ex-situ X-ray diffraction (XRD). Bi NS-1 with a high fraction of edge sites and defect sites exhibits excellent performance, and the current density is up to ca. 870 mA·cm⁻² in the flow cell, far above the industrially applicable level (100 mA·cm⁻²), with a formate Faradaic efficiency greater than 90%. In-situ Fourier transform infrared (FT-IR) spectra detect *OCHO, and theoretical calculations reveal that the formation energy of *OCHO on edges is lower than that on terraces, while the defects on edges further reduce the free energy changes (ΔG). The differential charge density spatial distributions reveal that the presence of defects on edges causes charge enrichment around the C–H bond, benefiting the stabilization of the *OCHO intermediate, thus remarkably lowering the ΔG.