A simple and new effective electrochemical method was used prior to reverse osmosis for seawater desalination. The influences of three main factors in electrochemical methods-current density, operating time and sedimentation time on the efficiency of pretreatment-have been investigated, It was shown that the electrochemical method is very effective for removal of turbidity. The qualities of the raw and the treated seawater have been measured using UV-Vis spectrometry. The morphologies and the particle size distribution of the resulted sludge have been characterized by scanning electron microscopy and a particle size analyzer, and the mechanism of the electrochemical method has been analyzed theoretically.