More and more evidence shows that lactic acid bacteria play an important role in improving calcium absorption and promoting bone health. However, there is a lack of systematic research on the mechanism by which lactic acid bacteria promote calcium absorption. In this article, the calcium absorption mechanism, the effect of lactic acid bacteria on calcium absorption and its mechanism are reviewed. Lactic acid bacteria promote calcium absorption mainly by 1) increasing intestinal absorption of vitamin D, thereby affecting the transcellular pathway of calcium absorption; 2) secreting phytase to increase the intestinal concentration of free calcium ions; 3) metabolizing prebiotics to produce short-chain fatty acids, thus reducing intestinal pH, increasing the surface area of microvilli, and affecting the signaling pathway of mineral absorption; 4) transforming lactose into lactic acid and short-chain fatty acids to increase the body’s absorption of calcium; 5) producing bioactive substances, increasing the content of soluble calcium in the intestinal tract and improving the bioavailability of calcium; and 6) directly or indirectly regulating bone metabolism and affecting bone homeostasis through the gut-bone axis. Lactic acid bacteria play an important role in promoting calcium absorption and maintaining bone metabolic balance, suggesting the potential of supplementation of lactic acid bacteria as a novel method to promote calcium absorption and prevent osteoporosis. This review lays the theoretical foundation for developing more efficient and targeted calcium supplements based on lactic acid bacteria.