Abstract: Rare earth fluoride molten salt electrolytic slag is not only an important secondary resource for rare earth recovery, but also very important for fluorine recovery and utilization. In this study, sulfuric acid leaching method was used to treat rare earth fluoride molten salt electrolytic slag to separate fluorine from rare earth, and the generated hydrogen fluoride was recovered by multistage absorption. The effects of leaching temperature, liquid-solid ratio, leaching time and sulfuric acid concentration on defluorination rate were studied. The results showed that under the conditions of leaching temperature of 360 ℃, liquid-solid ratio of 2:1, particle size of 58~75 μm, constant stirring speed of 300 r/min, and reaction for 3 h, the removal rate of fluorine could reach 95.28%, achieving the purpose of fluorine recovery. Finally, through the dimensional analysis of experimental data, the standard number equation of fluorine removal rate is obtained.