Aiming at the requirements of the thickness-controllable processing for the integral bottom of the launch vehicle tank, the mirror milling process was studied from the aspects of cutting force suppression and stability control. Through the milling force simulation analysis, the relationship between mirror milling process parameters and milling force was studied. The principle of selecting process parameters was proposed to ensure material removal rate by feed and cutting width and to control the cutting force by reducing the cutting depth. A method was proposed to measure the machining stability by compensating the axis fluctuation of the inner support and the influence of jet pressure of the inner support was studied. Taking the integral bottom of the new-generation launch vehicle as object, the process flow was designed, and the mirror milling path planning and post-processing were studied. Through processing of the integral bottom product, the thickness accuracy of 0.3 mm and maximum profile deformation of 3.2 mm were achieved, which effectively verified the processing capacity and effectiveness of the mirror milling process.