To study the flow characteristics of the vortex-type grit chamber and improve the sand removal efficiency, the flow characteristics and sand removal efficiency of the vortex-type grit chamber initially set up in a sewage pumping station were analyzed by RSM model and DPM model based on the numerical simulation method. In view of the shortcomings of the vortex-type grit chamber, the optimization scheme of adding deflector plate were proposed, and the flow characteristics and sand removal efficiency of deflectors in different schemes with different lengths were compared. The results show that the water flow in the vortex-type grit chamber presents a spiral shape due to the horizontal circulation and elevation circulation caused by wall barrier and impeller blade rotation. When the water flow enters the pool along the inlet channel, it has an impact on the rotating water flow in the pool body, and the inlet flow with high velocity shifts to the center of the pool under the action of pressure difference, which easily rolls away the sand particles near the center of the pool, affecting the sand removal effect of the vortex-type grit chamber. Adding a baffle at the end of the inlet channel can effectively reduce the impact of the inlet flow on the rotating water flow in the sand settling basin and make the water flow that hits the baffle turn down to the bottom of the pool, thus improving the sand removal efficiency. Comparing the three baffle schemes, the sand removal effect is better when the length of the baffle is 2 000 mm. The sand removal efficiency of 0.10, 0.15, 0.20 mm sand particles increased by 7%, 11% and 2%, respectively.