The tandem mill system of stainless steel pipe introduced by Shanghai Bao-Shan Iron and steel group from oversea is a kind of equipment with international standards and high productivity, it can roll steel pipe 250 ten thousand tons every year, its output value reaches about 16 hundred million yuan. And the tandem mill system requires the tact of different equipments be equal. It includes high-speed milling equipments, so it is demanded to have good productivity. In the practice of machining stainless steel pipe, its cutting speed is 140m/s(or 8482m/min), feed speed is about 100m/s, the material of tools is 65Mn quench steel, the material of workpieces are carbon constructional steel such as10, 20, 30, 35, 45 and low alloy steel such as 16Mn, 20Cr, 27SiMn, 35CrMn, 0.9MnV, 12CrMo, 15CrMo, Etc. Obviously, the property of tools is quietly different from the needs of the traditional theory. In fact, it has not only capability to work at high speed but also long tool life (about 12 hours). This paper is devoted to draw a cutting theory of abnormal milling at high speed from cutting phenomenon and effects in the process of abnormal high-speed milling, explain it and present the method to enhance the machining quantity.At first, this paper deals with the cutting model of the milling at high speed. The cutting equation of high-speed milling is presented under the discussed cutting conditions and the temperature distribute on the cutting zone is obtained from studying on thermal prosperity under high-speed milling. It is theoretical base to put forword the high-speed milling mechanism model.Obviously, the effect of material removing in the high-speed milling is different from common cutting. The mode of the high-speed milling has been founded and the theory of that one has been put forward according to analyzing the process of cutting. There are four effects in the process of high-speed milling according to analyzing the chip’s shape, it is the workpieces material’s heated stack effect, the material"s high-temperature soften effect, sameness effect of the temperature in cutting zone and tool’s heat release effect. The high-speed milling can be achieved only when numerical values of all effects reach a certain value. These effects make use of friction and extrusion to increase temperature of the area of work cutting and make the hardness and strength of work reduce obviously. At the same time, the temperature of cutting tool is kept under 300℃ and the hardness is invariable, which can carry out the multiplication of the ratio of tool hardness and work hardness to finish ultra high-speed cutting.The cutting abrasion of tools is the focus in cutting study. So this paper concerned with the particular analysis at the form and mechanism of which tools destroyed under the discussing conditions, especially deals with the action patterns of the mechanism stress and thermal stress in the cutting process and its results. Some problems discussed are the breakage of the tooth and fatigue of back face.On the basis of above studies, the work is aimed at examining the main factors which affect the high-speed milling and the optimize calculations of them. It especially carries out the analysis for the affect of the feed speed, tool angle and shape of tooth. Lastly, in this paper all above with theories and tests results have been explained.