Recently, many studies carried out to improve the performance of the pump with shape changes. In this paper, impeller optimization is performed to improve the pump performance. Design optimization techniques for the sludge pump impellers have been developed by using computational fluid dynamics (CFD) and optimal design theory. This paper describes the design optimization of a sludge pump impeller based on Response Surface Method (RSM) coupled with Navier-Stokes flow analysis. In particular, RSM which was based on the results of the design of experiment (DOE) helps to achieve the optimum point. In order to optimize the shape of the impeller, the thickness and the height of the blade were set as design factors. As a result, it was confirmed that the efficiency and the head were improved by 11.2% and 6.67%, respectively, compared to the referenced model.