It was taken as typical steelmaking fluorine-containing slag systems with the remelting electroslag, continuous casting mould flux and refining slag. The volatilization behaviour of each slag system was analysed by thermogravimetric (TG) and mass spectrometry (MS) detection. The results showed that the remelting electroslag volatilized significantly above 1300°C and the volatiles were mainly CaF2, MgF2 with a small amount of SiF4 and AlF3; the continuous casting mould flux volatilization was divided into two stages, in the first stage (500°C∼800°C), CaF2 and Na2O reacted to form NaF, and in the second stage (greater than 1200°C), the CaF2 evaporation was highlighted; for CaF2-CaO-based refining slag, the volatilization was the most significant at the eutectic point 84% CaF2–16% CaO, and the volatility can be reduced by adding 5% SiO2. This research will be guiding significance for the composition and performance control of fluorine-containing slag and metallurgical environmental protection in the steelmaking process.