Draw solution assisted reverse osmosis (DSARO) process is suggested and mathematically modelled in this study. The main concept of the process is osmotic pressure reduction in the RO process by utilizing draw solution which has lower concentration than seawater. Since the pressure requirement of the DSARO process is in the range of BWRO process, the plant capital cost data in BWRO process can be used for cost estimation model. The cost estimation results shows that the specific water cost in DSARO process is more than 10% lower than that of conventional RO process. So the DSARO process can be economically feasible.