Abstract Based on the research on the 635 spillway rectification project in Xinjiang, a 6-factor and 3-level orthogonal design of experiment is performed for the spillway with rough strip energy dissipator(R-SED)by using orthogonal design principle, and the instantaneous stream velocity and water depth in 18 typical cross-sections are obtained. A model for mass discrete coefficient Cm is established by means of discrete element method for bend, and a range analysis is performed on the experimental results in terms of energy dissipation rate η. To generalize the evaluation method for diversion effect, two dimensionless factors Rd and Rs, are defined and the correlation between layout parameters and engineering parameters is analyzed further. The results show that the mass dispersion coefficient Cm can objectively reflect the diversion effect of R-SED. As far as the influence of the index Cm is concerned, the influence of engineering parameters on the index is dominant compared with the layout parameters. Naturally, the determination of engineering parameters should take full account of flow pattern in practical engineering. Since both Rd and Rs are all dimensionless, the evaluation method based on them is universal for diversion effect of general spillway rectification projects.