Hydraulic jump is one of the rapidly varied flows that different elements can be employed to control it in stilling ?basins. The purpose of this study is optimal design of obstacles at USBR II stilling basin of Nazloochay dam model. For this purpose, the obstacles at the end chute with thicknesses and heights of 0.5, 1, 1.5 ?and 2 m and 2, 3 and 4 steps at the end USBR II stilling basin have been considered. Then for the most optimal state, the ?pressure, water surface profile, turbulent kinetic energy, and turbulent kinetic energy dissipation investigated for ?discharging 830 m3/s by using K-? and RNG turbulence model and VOF method. According to changes in water ?height, obstacles selected with heights of 1 and 1.5 equal of standard state at the end chute and 3 steps at the end stilling basin?. The comparison of numerical and experimental values of water surface and pressure profiles showed that ?numerical model has good agreement with experimental results. Also, hydraulic jump on adverse steps at the end stilling ?basin increase energy dissipation and stability of hydraulic jump. In addition, numerical model can be used to model ?stilling basins and measuring non-measurable parameters in laboratory.?