Freeform optics are greatly in demand for use in next-generation space cameras for achieving higher optical design freedom as compared with the commonly used spherical and aspherical elements. Freeform optics have the advantages of excellent optical performance and simplified system structure. The development of optical remote sensing technology imposes higher requirements on these optics. Therefore, a series of optimization procedures of grinding process parameters for zerodour mirrors were conducted, and the grinding of a 300 mm aperture freeform mirror was completed using the optimized process parameters. The results show that the surface figure of the mirror increases to 8.89 μm PV, and the depth of the subsurface damage layer reduces to less than 18 μm. Realizing high precision and low damage grinding of freeform optics is of great significance for reducing the workload of subsequent lapping and polishing.