In the fabrication of cylindrical single-crystal silicon mirrors, there are many disadvantages, including low removal efficiency, poor figuring accuracy, and difficult surface-quality controllability. Herein, ion-beam figuring (IBF) with a titled incident beam was proposed to optimize the process technology of fabricating cylindrical single-crystal silicon mirrors. First, the theoretical model of the tilted incident IBF removal process was established to determine the relationship between removal efficiency and incident angle. Second, when the ion beam was incident obliquely, the mechanism of the microcosmic morphology was also analyzed to determine the relationship between surface quality and incident angle. Finally, the removal efficiency and surface quality were comprehensively optimized to obtain the optimal incident angle for the tilted incident IBF process, and an innovative process technology based on tilted incident IBF was proposed. A convex cylindrical single-crystal silicon mirror with dimensions of 100 mm×100 mm was tested using the tilted incident IBF process. The total machining time was reduced by 53.7% using the titled incident incident IBF process compared with that using the vertical incident IBF process. Experimental results indicate that the tilted incident IBF process can not only improve the machining efficiency but also obtain high accuracy and quality surface.