Glass material has many fine chemical properties and is widely used in high-technology fields such as aerospace and biomedical. But it is also a typical hard processing material due to its brittle and hard nature. Conventional mechanical processing methods will cause low efficiency, poor surface quality, and even surface damage when processing such materials. In order to get good surface quality, glass material must be processed plastically. This paper adopt micromilling method in processing soda lime glass, analyzed the micromilling mechanism in processing glass material, obtained the critical brittle–ductile transition condition under the consideration of size effect. Processing parameters’ range was obtained according to milling experiment in which ball-end mill was used. Surface roughness was measured and tool wear was observed simultaneously. Experimental results shown that plastic processing of glass material which brought good surface quality can be achieved by changing processing parameters and tool parameters.