The fabrication of small size aspheric optical surface, which made of hard brittle materials, usually uses optical cold processing. However, it is difficult to achieve the ideal requirements of the surface accuracy and roughness. In order to solve this problem, the masked ion beam figuring method is used to etch the one-dimension structure on the plat surface which made of hard brittle material. The results show that the expected surface profile is acquired and meanwhile mainly kept the original roughness and mid-frequency. It provides a possible way for fabricating small size aspheric optics which made of hard brittle materials.