Abstract: The particle size of the carbide slag from Nanjing is relatively fine with particle size of 86.81% -0.074 mm，CaO content can up to 69.83%，and the major impurities are SiO₂，C，etc.Main impurities affect the whiteness of products are carbon and iron bearing minerals.To obtain high-quality carbide slag concentrate，the process of desilication using dodecylamine，decarbonization using kerosene all by reverse flotation and deferrization by high intensity magnetic separation for purifying -0.425 mm carbide slag was adopted.The results indicated that:For the products that have been removed the coarse fraction (+0.425mm)，with the reverse flotation process of one roughing，one cleaning and one scavenging adopted for desilicationg，then one stage reverse flotation for decarbonization，finally one stage high intensity magnetic separation adopted for deferrization，high-quality concentrate with CaO grade of 72.83%，CaO recovery of 81.57%，products whiteness of 90.14% was obtained which met the quality requirements of high-quality carbide slag concentrate.

Key words: Carbide slag, Reverse flotation, High intensity magnetic separation, Whiteness