Electrochemical energy storage is flexible and efficient, and it is an important direction for the development of large-scale power energy storage technology. Liquid metal battery (LMB) uses liquid metals and molten inorganic salts as electrodes and electrolytes, respectively, to fundamentally avoid the life-limiting problem of traditional batteries. LMB has the advantages of long life, low cost, and large capacity, and has broad application prospects in the field of power system energy storage. This paper mainly introduced the working principle of LMB, focused on its development history and important research progress, and pointed out the limitations and challenges of existing battery systems. On this basis, the key development directions of LMB were discussed and clarified.