In response to the erosion problem in the flow channel of glass fiber reinforced plastic (GFRP) floating ball valve during use, Fluent software was used to simulate and analyze the gas-solid two-phase flow field of the flow channel of DN50 ball valve. The movement phenomenon of the internal flow field of the ball valve was studied, and the variation law and influencing factors of the erosion rate on the wall of the ball valve were analyzed.The correctness of the model is verified by experimental data validation. The research results showed that when the relative opening of the valve ball (CV=20~80), The circulating flow inside the ball valve will cause a certain amount of energy loss, and an increase in flow rate and a decrease in the relative opening of the valve ball will increase the energy loss of the fluid in the flow channel; Increasing the inlet velocity can reduce the area of erosion in the flow channel; On the other hand, the erosion rate on the wall is opposite. As the particle diameter increases, the erosion rate on the wall first decreases and then increases; The change in relative opening of the valve ball changes the flow channel structure of the ball valve. When the particle diameter is d=180 μm, adjusting the relative opening of the ball valve has little effect on the wall erosion rate, and the highest erosion rate is 7.069×10-11 kg/m2·s. When the particle diameter is d=850 μm, increasing the relative opening of the ball valve CV=20 to CV=80 can reduce the wall erosion rate by 64.3%.