Abstract: Lepidolite ore is an important lithium resource, and its development and utilization have drawn increasing attention with the continued growth of lithium demand; however, challenges remain in terms of lithium extraction efficiency and process control. To improve the conversion and leaching efficiency of lithium from lepidolite, this study takes lepidolite ore from Inner Mongolia as the research object, adopts a suspension sulfation roasting–leaching process, systematically investigates the effects of additive type and dosage, roasting temperature and time, liquid−to−solid ratio, and leaching temperature on lithium leaching efficiency, and combines thermodynamic calculation, XRD, and SEM characterization to analyze the mineral phase transformation and microstructural evolution during roasting. The results show that under the conditions of roasting temperature 750 °C, roasting time 30 min, Na₂SO₄−to−ore mass ratio 0.5, liquid−to−solid ratio 5, and leaching temperature 80 °C, the lithium leaching efficiency can reach 92.76%. Thermodynamic calculation indicates that the sulfation roasting reaction of lepidolite is endothermic and requires external heat input to proceed in the range of 750–950 °C. XRD results show that the characteristic peaks of lepidolite in the raw ore are significantly weakened or disappeared after roasting, and phases such as Na₂SO₄, NaAlSi₃O₈, KAlSi₃O₈, Na₂Si₂O₅, and quartz appear in the products, indicating that Na₂SO₄ participates in the destruction of the aluminosilicate framework of lepidolite and the formation of sodium aluminosilicate phases. SEM characterization results show that cracks and pores form on the particle surfaces of the product roasted at 750 °C, and the structure is relatively loose; when the temperature is further increased, localized densification and sintering are enhanced, which is unfavorable for maintaining the reaction interface. The research results can provide a reference for process optimization and mechanistic understanding of lithium extraction from lepidolite by suspension sulfation roasting.