This paper examined the erosion characteristics of the curved core surface of the ball valve when subjected to the two-phase flow of sand-carrying high-pressure gas. The Computational Fluid Dynamics (CFD) method for joint analysis was used to establish the erosion simulation model, the critical factors, such as the ball opening degree, ball diameter affecting the flow field and erosion distribution of the gas-solid two-phase flow were analyzed. The flow field simulation results show that the gas velocity changed violently after entering the ball valve due to the reduction of the cross-sectional area, and the maximum velocity at the turning position increased gradually in conjunction with the decrease in opening degree, while remain unchanged with the increase of ball diameter. Moreover, the particle trajectory show that particles flowing in from the right straight pipe section mainly colliding with three areas including outer wall surface (zone 1), upstream wall surface (zone 2) and the outlet pipe section near the lower wall of the ball valve (zone 3), which were consistent with the location of that particle wall collision happens. The comparative analysis of the maximum erosion rate under different influencing factors shows that decreases with the increase of the ball diameters the opening degree and ball diameter. This research provided theoretical guidance to the erosion analysis of the ball valve core by the two-phase flow of high-pressure sand-carrying gas subjected to the changes in a variety of crucial parameters. This paper also presented a field application value for the design and maintenance of the ball valve in the natural gas pipeline.