This study presents channel design of a CDI stack to achieve high removal efficiency in a large scale by applying parallel flow structure with a concentrated stream. The flow pattern in the stack was simulated by COMSOL Multiphysics program. To prove the salt removal performance, a unit cell and 20 cell stacks were tested at a flow rate condition of 18 ml/min and 360 ml/min, respectively. The removal efficiencies of the unit cell and the 20 cell stacks were obtained as 70.8 % and 75.6 %, respectively, with 100 mg/L sodium chloride solution. During the operation of cell test, water pressures of unit cell and 20 cell pair stack maintained in the ranges of 1.1 psi and 1.3~1.5 psi, respectively. It was demonstrated that the parallel cell structure with two concentrated streams can be employed in a large scale CDI for salt removal.