Abstract: To effectively control the quality of combed pure yarn evenness, and to comply with the market development trend of varieties of transformation and quality upgrade of wool spinning products, in this article, through analysis, derivation of the theory of spinning technology and experimental demonstration, is derived for the calculation formula of raw material of wool diameter design value, the calculation formula of theoretical sliver evenness coefficient of variation of wool yarn, and the calculation formula used to rapidly determine the ratio of two kinds of wool top. Article is put forward the semi-product evenness quality control process for fore-spinning based on it’ s quality index number, with according to the latest Uster statistical bulletin to forecast and analysis the quality level of the wool yarn evenness, and to make the wool assorting schemes get timely feedback, adjustment and optimization; At the same time, draw lessons from foreign advanced experience, through drawing the sliver evenness quality analyses graph for fore-spinning semi-products to track and analysis the quality data of the sliver evenness, and to make the production technical schemes get timely feedback, adjustment and optimization. Therefore, quality control technology guided by the sliver evenness quality index number can be more scientific and effective to achieve the quality objectives of the combed pure wool yarn.