Abstract: Abstract: Filters have high energy consumption, high cost and high water consumption and other shortcomings. In order to solve this problem, gravity sinking and filter tank for drip irrigation with river water (GSFTDIRW) is proposed, which consists of sedimentation tank, clear water tank and sewage tank. The flow is the key factor influencing the separation efficiency of water-sediment and the flow field of wate-sediment. This study investigated the influence of flow rate on the GSFTDIRW. A physical experiment was carried out in the hydraulic experiment hall of Xinjiang Institute of Water Resources and Hydropower Research. The parameters such as water depth, flow velocity and sediment concentration in the GSFTDIRW under flow rate of 0.05 m3/s were measured. The model was set up according to the model size used in the physical experiment in the gambit drawing software. Meanwhile, the boundary conditions were set in the gambit drawing software. Then the parameters were set in the Fluent software. Simulated values were processed by tecplot software. By comparing the experimental values and simulated values, it was shown that the porous media model was reliable in simulating the filter mesh. It was feasible to simulate the internal flow field in GSFTDIRW using the standard k-ε two-equation model and the mixture model. Based on these, the flow field of water-sediment two-phase flow was simulated in the GSFTDIRW under 4 different flow rates. By comparing the distribution of flow velocity along the length, the distribution of water velocity along water depth and the separation efficiency of water-sediment, it was found that the appropriate flow rate was in a range of 0.05-0.2 m3/s when the sedimentation tank was 25 m in length, 1.5 m in width, 0.80 m in height, slope 1%, and lateral overflow weir 5 m. At the same time, the average flow velocity of sedimentation tank is 0.053-0.19 m/s. The smaller the influent flow was, the smaller the velocity variation was. This was more conducive to sedimentation. The sediment concentration was less than or equal to 1.65 kg/m3 in the clear water tank, and the total water-sediment separation efficiency was not less than 72.5%. Under the different flow rates, the flow velocity change along the sedimentation tank could be divided into 3 stages: increasing rapidly, decreasing slowly and decreasing rapidly. The velocity of flow in the clear water tank was opposite to that of the sedimentation tank, and the flow velocity decreased along the path. Under the influence of inlet, outlet and solid boundary, and lateral overflow weir, the distribution of flow velocity along water depth was different under different flow rate in the GSFTDIRW: the distribution of velocity along the depth of water at the locations far away from the water inlet, outlet and lateral weir contained 3 stages when the flow rate was 0.05 and 0.1 m3/s: rapid increase, slow decrease and constant. However, the distribution of velocity only included the rapid increase and constant stage in clear water tank.