Sepsis is a life-threatening organ dysfunction caused by the host's imbalance in response to infection, which is still the leading cause of death in critically ill patients. In recent years, studies have found that vitamin D deficiency or insufficiency is common in critically ill patients, especially sepsis. The relationship between vitamin D and sepsis has attracted more and more attention. The mechanism of vitamin D in sepsis is described from the aspects of immune regulation, inflammation regulation, endothelial cell protection, carbon monoxide regulation, and receptor gene polymorphism, by analyzing the related literatures of vitamin D and sepsis in recent years in order to provide new ideas for clinical diagnosis and treatment of sepsis.