In view of the current low rate and low level utilization of steel slag in China, analyzes the physical and chemical properties of steel slag and its recycling technical defects. On the basis of "particle beds comminution" principle, puts forward a new technique of grinding steel slag with horomill. Studies in detail the structure and the grinding principle of horomill and the process flow to make steel slag powder. The results show that using horomill to grind steel slag has advantages of low working press, high efficiency, low energy consumption and so on.