Abstract: The large high-precision sphere is the key core part of the large high-grade hard seal valve, it difficult to solve the influence of the self-weight of the spherical parts on the processing precision by traditional processing methods. The precision and surface quality of spherical parts are hard to meet the requirements of hard sealing. Therefore, a large vertical spherical grinder is developed and the main configuration and working principle of the machine are analyzed. By analyzing the principle of the generating grinding method, a mathematical model for the grinding trajectory of SMG240 vertical spherical grinder is established. The grinding trajectory was simulated and simulated with Ansys software. The main parameters affecting the grinding trajectory and grinding quality were studied. The research highlights specific operational conditions such as clockwise rotation of both the grinding head and sphere, the ratio of grinding head speed to sphere speed is 30, and the number of sand strips is sixteen, the grinding effect is optimal. Finally, grinding experiments were conducted, achieving a spherical precision of ±0.015 mm and a surface roughness Ra≤0.4 μm for a large 2 000 mm diameter spherical body. The effectiveness of the grinding parameters was verified, the high-precision and high-efficiency grinding of large-scale high-precision spherical bodies is realized successfully, and the grinding quality is improved.