Abstract: To tackle the problems regarding low efficiency of sizing and low comprehensive utilization rate of gasification slag, a sizing process using high-efficiency classifying cyclone in combination with compound sizing screen is developed based on result of analysis of the ploysiochemical property of gasification slag. The influence on slag sizing effect produced by different sizing processes and structural parameters are brought to light through testing means. Study result shows that the proposed combined slag sizing process can not only work with a high efficiency but also offers the special merits of being simple instructure, less in occupation of floor space, easy to operate and low in maintenance cost. Application of the sizing process breaks the technical bottleneck encountered in sizing of gasification slag and provides a technical support for realizing high-efficiency resource utilization of such a material.