In order to study the hydraulic characteristics of the unilaterally divergent stilling basin, the RNG k-ε two-equation turbulence model was combined with the VOF method to calculate the water flow in the stilling basin. The calculated surface line, pressure and flow rate are compared to the model test results. The results of comparative analysis show that the numerical simulation is basically consistent with the results obtained by the model test. The in-depth analysis shows that the water flow produces a vertical axis vortex at the diverging side tail; the horizontal axis formed by the leaping roll moves upstream in the diverging side, and the water jumps to the tail. The shaft moves downstream on the diverging side; The turbulent energy may reflect the distribution of the pulsating pressure to a certain extent; the pulsating pressure on the front plate of the reverse arc segment and the stilling basin is large, and the design can strengthen the protection of these regions.