Lithium ore smelting slag is a major bulk solid by-product generated from conventional pyro-hydrometallurgical lithium extraction processes. Developing efficient resource utilization and high-value conversion technologies for this material is crucial for reducing China's dependency on external lithium resources, ensuring the stability and security of the new energy industry chain, and promoting green, low-carbon development. Current research has employed various techniques, such as combined pyro-hydrometallurgy and alkali roasting, to enhance lithium leaching kinetics and enable the co-recovery of associated critical metals such as rubidium (Rb), cesium (Cs), and aluminum (Al). Specifically, pyro-hydrometallurgical approaches can achieve lithium leaching efficiencies exceeding 97%, while subsequent processing of recovered lithium salts via molten-salt electrolysis or thermal reduction, followed by vacuum refining, can yield lithium metal with purity exceeding 98%, potentially reducing energy consumption and environmental pollution. Additionally, solvent extraction and electrochemical methods have shown considerable potential for selective lithium recovery. For associated metals such as Rb, Cs, and Al, high-temperature roasting followed by acid leaching can achieve Rb recovery efficiencies of up to 93.09%, although this method faces challenges regarding energy consumption and product purity. Beyond metal recovery, lithium slag demonstrates significant potential in the production of value-added construction and functional materials such as high-performance ternary geopolymers, cement, and molecular sieves. For instance, under optimized mix designs, incorporating 5% lithium slag as a supplementary cementitious material can reduce energy consumption and achieve 28-day compressive strengths exceeding 80 MPa, demonstrating excellent engineering applicability. Furthermore, lithium slag can be synthesized into environmentally friendly materials such as ternary geopolymers and NaX zeolites. The former exhibits high immobilization efficiency for various heavy metals, while the latter possesses a well-defined structure and superior adsorption performance. Despite these advances, several challenges persist, including incomplete lithium extraction, low recovery efficiencies of critical metals, and the lack of standardized processing systems. Accordingly, this review systematically analyzes the physicochemical characteristics of lithium smelting slag, including its chemical composition and occurrence modes. It summarizes mainstream recovery techniques for valuable metals (Li, Rb, Cs) and evaluates recent advances in producing high-value-added products. Finally, the study outlines a sustainable technology framework centered on "source reduction, low-carbon processing, and end-stage high-value conversion," emphasizing rapid activation, multi-component selective separation, and full-process system integration. This work aims to provide theoretical guidance and mechanistic insights to support the development of green recycling technologies for lithium ore smelting slag.