A numerical simulation of the characteristics of flushing during the venting process for a hydraulic self-cleaning system in a storage tank was conducted using computational fluid dynamics (CFD) method. An analysis was conducted to analyze how the opening time of the gate and changes in water level within a storage tank influence the flow characteristics during venting flushing processes and the flush effect of sediment at the bottom of the system. The nonlinear regression fitting formula between the scour rate and the water storage height was constructed. The results show that the maximum average flow velocity of venting flushing decreases with the increase of gate opening time and increases with the increase of water storage height. The velocity attenuation of venting flushing flow mainly occurs in the front half of the corridor, and the flushing shape of the corridor sediment after venting flushing is V-shaped distribution. The scouring rate of the venting flushing decreases with the increase of the gate opening time. At 1.5 m water storage height, when the gate opening time increases from 10 s to 20 s, the scour rate decreases from 46.27% to 35.23%. The scour rate of venting flushing increases with the increase of the water storage height. With the gate open for 10 seconds, the scour rate increased from 4.83% to 58.67% as the water storage height rises from 0.5 m to 2 m.