Steelmaking slag is a by-product in considerable volume and a valuable material for various applications. In general, steelmaking slag is an alkaline compound of CaO, Fe2O3, and SiO2. However, its characteristics vary depending on the feedstocks and process of steelmaking and cooling method of the slag. To utilize the by-products effectively, this study investigated the characteristics of steelmaking slags in recent from Wuhan Iron & Steel Co. Ltd. The results showed that the slags mainly consist of the oxides of calcium, iron, and silicon, with low contents of magnesia, alumina, and manganese oxide. The major mineral phases include belite, calcium ferrite, calcium hydroxide, wustite, quartz, while containing less alite. Thermogravimetry analysis indicated the weight loss from ambient temperature to 800°C is 8% in total. Melting test showed the glass transition temperature is between 1300°C and 1350°C, flow temperature is about 1400°C. The slags are a typical glass-ceramic composite.