To clarify the effects of different flow-sediment conditions and channel slopes on the sediment discharge characteristics in a desilting channel with a swirling flow generator, numerical simulation was conducted using the Realizable k-ε turbulence model combined with the Discrete Phase Model (DPM), based on experimental findings. The study investigated changes in sediment trapping efficiency and sediment discharge under varying channel slopes, inlet flow velocities, inlet water depths, and median sediment diameters. The results show that after installing a sand vent with a swirl chamber in the channel, the sediment concentration at the downstream channel bottom decreased from (33~46) kg/m3 to (0.3~0.8) kg/m3, indicating a high sediment removal efficiency of the swirling desilting channel. When flow-sediment conditions and channel slope were altered, sediment settling conditions changed accordingly, thereby affecting the sediment trapping efficiency. As the channel slope increased from zero to 1:500, the sediment trapping efficiency decreased by approximately 2.32%. When the inlet flow velocity increased from 0.80 m/s to 1.28 m/s, the sediment trapping efficiency decreased by 8.03%. An increase in the water depth from 0.110 m to 0.176 m led to an 8.95% reduction in sediment trapping efficiency, while an increase in the median sediment diameter from 0.16 mm to 1.25 mm resulted in an 8.68% increase in sediment trapping efficiency. Increases in slope, flow velocity, and water depth reduced the sediment settling time in the channel, whereas an increase in the median sediment diameter enhanced the settling velocity, leading to corresponding changes in sediment trapping efficiency.