To obtain CaO slag-making material excellent in quick slagging without using fluorite by blending powdery lime or dolomite as a raw material and a specified ratio of aluminum ash being refining slag in the aluminum melting, mixing them and press-forming the mixture.

The blending ratio of the aluminum ash is 5-60 wt.% and after pulverizing the lime into fine powder, this fine powder is solidified with a high- pressure molding means. The lime shaped after passing once the pulverizing process, has excellent thermal conductivity and can be made to the quick slagging by contacting with molten steel in a furnace and slag-making refining in the short time can be executed. The aluminum ash is blended into the lime and mixed and press-formed, and when this mixed solid is added into a high temp. furnace at ≥1500°C, a low melting point calcium aluminate is generated at the boundary of both components of CaO and Al2O3 and the slagging is easily progressed. CO2 gas is generated by blending 1-20 wt.% time granular calcium carbonate as the slag-making activator to activate the slagging. To the slag having high CaO calcium aluminate composition, fluorite is desirable to be added at 1-20 wt.%.