Abstarct: The main reasons used of the stepped spillway is energy dissipation and flow aeration. Energy dissipation in stepped spillway is to reduce the cost of building the stepped spillway stilling basin and flow aerated is to prevent cavitation damage. In the spillway elementary steps next to the boundary, turbulence is generated and the boundary laxyer grows until the outer edge of the boundary laxyer reaches the free surface. When the outer edge of the boundary laxyer reaches the free surface, the turbulence may initiate natural free surface aeration. Therefore, the flows over this type of spillways is highly turbulent, and the turbulence modeling has a significant impact on results in simulation of its. Ansys Fluent software is used for to model the flow. This software uses the finite volume method to solve the governing equations. Volume of fluid (VOF) method used for Free surface simulation. Standard k-ε, RNG k-ε, Realizable k-ε, standard k-ω and SST k-ω turbulence models are compared. Siah Bishe Bala dam spillway experimental model results used for verification of the simulation.The horizontal pressure profile steps plotted and simulation results are compared with the experimental. The results show that three models RNG k-ε and the standard k-ω and SST k-ω are closer to the experimental data. RNG k-ε model in the near wall regions (the appropriate wall function should be selected for this model) and the standard k-ω model in the regions away from the wall and free shear flows are weak. SST k-ω model in the near wall regions as the standard k-ω model and in the regions away from the wall as standard k-ε model acts, therefore, this model compared to the standard k-ω and RNG k-ε models is less limitation and is more suitable. The energy dissipation in discharge per unit width, 4.6, 7.5,9 and 10.15 in slope 21.18˚ has been investigated. The results show that the highest rate of energy dissipation 85.86 and the lowest 21.18 percent. Also rate of energy dissipation is reduced by increasing the the discharge. Therefore, significant energy is wasting in stepped spillway and this can reduce construction costs or even eliminate the stilling basin.