The Euler model was used to simulate the solid-liquid two-phase flow in the double-storey sedimentation tank, and the effects of length and depth proportion of upper and lower storeys on hydraulic state, particle sedimentation, and turbidity removal effect were revealed. The results show that when the length is moderate and the proportion is close to one, the particle concentration at the outlet is relatively small and the difference in flow ratio is small, which basically meets the design. With the reduction of the length, it is difficult for the concentration of the suspended matter in the rear section to settle effectively. When the length is further increased, the solid particles have basically settled to the bottom before reaching the rear. When the proportion of the upper and lower stories is different, the water depth is greatly different, and the flow ratio is greatly different. When the depth of the upper storey is small, the particles deposited on the upper partition have a greater impact on the water quality of the outlet. When the depth of the lower storey is small, the overflow flow is reduced and the velocity is large, which is not good for the sludge deposition.