Production of high value-added chemicals and fuels from carbon dioxide (CO_2) is an important technology to achieve zero carbon emissions. However, how to efficiently and sustainably convert carbon dioxide into higher value long-chain molecules is still a challenge. Compared with traditional thermochemical techniques, electrocatalytic reduction can achieve high product selectivity under milder conditions, and can also be coupled with bioconversion techniques to convert short carbon chain molecules into long carbon chain products with higher added value. This paper reviews the state of the art of key factors affecting electrocatalytic CO_2 reduction performance, including electrodes, catalysts, ion exchange membranes and electrolytes. By adjusting the electronic structure, surface structure and coordination environment of the copper-based catalysts, the carbon-carbon coupling reaction can be effectively strengthened, and the Faraday efficiency of C_2+ products can be significantly improved at ampere-level current density. Furthermore, the research progress on the coupling of CO_2 electroreduction with microbial conversion to extend the carbon chain is reviewed, which mainly illustrates the advantages and challenges of this coupling technology from the perspectives of in situ and ex situ coupling modes.