Flow electrode capacitive deionization (FCDI) represents an improvement of the conventional capacitive deionization technology (CDI) and is of great relevance for industrial applications by providing higher desalination performance and sequential operation. The electrode materials (Double Layer capacitive materials and pseudo-capacitive materials), device configuration, and operation mode all have an important impact on the flow electrode capacitive deionization process. In this review, we review the background of flow electrode capacitive deionization, the composition of electrode active materials, the operation mode, the new device configuration, the application in the environmental field, and finally we provide an outlook on the future development of FCDI.