The flow characteristics of the stepped spillway is simulated by DualSPHysics in order to study the energy dissipation law and find the optimal parameters of the stepped spillway. Here, the applicability and accuracy of the smoothed particle hydrodynamics(SPH) method in the water flow simulation of the stepped spillway is verified through comparative analysis. Then, the energy dissipation law of the stepped spillway is studied by establishing a total of 288 working conditions with different single-width flow rates, stage gradients and the number of steps. The results show that the energy dissipation rate of the stepped spillway is negatively correlated with the single-width flow rate when the other parameters are constant; the number of steps has no significant effect on the energy dissipation rate of the stepped spillway, but there is a certain step number when the energy dissipation rate of the stepped spillway reaches the maximum value. According to the simulation results, the number of steps corresponding to the optimal energy dissipation rate is in the range of 78-81 steps. This conclusion has a certain referential value for the practical engineering.