The electrocatalytic CO2 reduction reaction (CO2RR) into hydrocarbon products is one of the most promising approaches for CO2 utilization in modern society. However, the application of CO2RR requires optimizing state-of-the-art catalysts as well as elucidating the catalytic interface formation mechanism. In this study, a flower-like nano-structured Bi catalyst is prepared by a facile pulse current electrodeposition method wherein the morphologies could be accurately controlled. Interestingly, nano-structured Bi is inclined to generate Bi2O2CO3 in the air and form a stable Bi2O2CO3@Bi interface, which could enhance the CO2 adsorption and conversion. In-situ Raman spectroscopy analysis also proves the existence of Bi2O2CO3 on the electrode surface. In a practical CO2 reduction test by a flow-cell reactor, the Bi2O2CO3@Bi electrode delivers a high faradaic efficiency of the CO2 to formate/formic acid (~90%) at −1.07 V vs. reversible hydrogen electrode (RHE) with no obvious decay during more than a 10 h continuous test. The introducing surface Bi2O2CO3 in nano-structured Bi supports a promising strategy as well as facile access to prepare improved CO2RR electrocatalysts.