Abstract: The RNG κ-ε turbulent model and dynamic mesh technology were applied to simulation of the unsteady flow of the flaring gate pier and the stilling basin during the radial gate opening. Six different total opening times were used to achieve the detailed hydraulic properties of different opening velocities. The opening velocities of the radial gate were homogeneous of every total opening time. The relationships between the opening velocities and pressures, flow velocities and other hydraulic characteristics were obtained by using six corresponding total opening times. Hysteresis effect was apparent while the total opening time was relatively small, and a water surface profile corresponding to different relative openings was also lower than those of other total opening times. The maximum flow velocity appeared at the ogee section of the overflow weir at the opening process no matter which total opening time was. The maximum velocity and the pressure on the impact region were much larger than the corresponding value at a constant situation. The slab of the ogee section and stilling basin was divided into three regions according to the distribution of pressurs; the relationships between the maximum pressure and the opening velocity was obtained. The velocities and the maximum pressure on the impact region in the stilling basin were much higher than those corresponding to the constant conditions while the opening velocities were relatively lower. The maximum pressure and differences between the maximum pressure on the impact region and an average pressure of the adjusting region increased with the increasing of the opening velocities, and fell to a normal value after long time. A gentle increase in pressures and other hydraulic characteristics would appear under the lower opening velocities. The water surface profile and other results of numerical simulation were in good agreement with the model test data, which shows that the numerical method is reliable. The analysis results can provide an important basis for operation of the similar radial gate located on the hydroproject.