In this work, carbon electrode modified polymer membrane and free-standing polymer membranes are applied for desalination via capacitive deionization with microporous activated carbon. The desalination performance under different concentrations (20 mM and 600 mM) of feed water and different voltage operation mode (zero-volt and voltage-reversal operation). For the ion exchange membrane coating under 20 mM NaCl solution at a cell voltage of 0/+1 V, the desalination capacity reached 22.7 mg/g at the charge efficiency of 142.1%. In the case of the free-standing membrane, under 600 mM NaCl solution at a voltage range of −1/+1 V, the desalination capacity reached 26.0 mg/g with a charge efficiency of 61.5%. These results not only show the possibility of membrane capacitive deionization (MCDI) application in seawater desalination but also reveals different ion transport mechanisms of the coated membrane and free-standing membranes under different molar strength of feed water.