The optimization approach is common approach to solve complex PSI issues. Most researches on the optimization approach focus on the solution method of the optimization model and improving modeling efficiency. In this paper, we give our effort on the influence of estimated pollution range on the groundwater PSI problem and discuss the efficiency and accuracy of 1D and 2D PSI problems. The estimated pollution range of PSI problem could affect how much calculated time would be consumed. The bigger the estimated range is, the more time is consumed. Increasing the dimension of the PSI problem will increase the estimated range greatly, and leads to a great time consuming. A slight movement of the estimated source in the direction perpendicular to the major migrate direction leads to big bias between the calculated source location and the real location. The chance that optimization model falls into the local optimum location is growing in the major migration direction.