As an emerging desalination technology, flow-electrode capacitive deionization (FCDI) has aroused extensive attraction due to its advantage of pseudoinfinite adsorption capacity. However, some problems still remain in the traditional FCDI devices, i.e., its streaming and seeping quality which has severely limited the progress. Herein, some improvements were achieved by changing the direction of saline water in spacer. Furthermore, the Archimedes spiral flow channel model was introduced to improve the flow behavior of carbon slurry in the FCDI unit cell for the first time, which has vastly boosted the desalination performance of FCDI devices. The computational fluid dynamics (CFD) simulation revealed the more uniform velocity distribution and longer residence time of carbon slurry in spiral flow channels to enhance the desalination, while the flow rate of carbon slurry in a straight line is faster but slower in the corner of serpentine flow channels, causing a negative effect on the desalination performance. After long-term continuous desalination in 3.5 g L–1 NaCl solution at 2.4 V, 99.88% of salt removal efficiency was achieved with a superior salt removal rate of 4.06 μmol cm–2 min–1 and 98.9% charge efficiency for the spiral flow channel FCDI device, demonstrating a stable desalination performance.