Abstarct: In this research, the shape of hydropower intakes was optimized by optimality criteria method to reduce the energy loss. The optimization criteria was streamlining and the optimization variables defined as solid boundaries coordinates. Since some aspects of intakes are not specified in the design procedure, proposing a numerical method to such designs was the main goal of this research. To optimize the shape of intakes by optimality criteria method a computer program, called Streamlining Programming Code (SPC), was developed in C++ programming language to streamline the cross sections of transitional sections by solving potential flows in order to obtain the streamlines coordinates and maps a selected streamline to the solid boundaries. To verify SPC, OpenFOAM software was used and modeled the potential flow of a contraction. The results showed that SPC has a good agreement with OpenFOAM software. So after validating the results of OpenFOAM by a similar research in turbulent modeling, the results obtained from OpenFOAM was validated. Finally, for optimizing the shape of intakes, as contractions have similarity with the intakes in horizontal section, first a contraction optimization was carried out. By optimizing the contraction defined in this research, the method used for shape optimization was confirmed to have the ability to present the optimum shape in this field. To optimize the shape of intakes, results from SPC was compared with recommended shapes of USBR and Indian Standard. The results illustrated that the shape obtained from SPC, enhanced the performance of intake about 2 percent in comparison with recommended shapes. In conclusion, the results demonstrated that the method used in this research has the ability of optimizing the hydraulic structures and different applications in the relevant fields.