Abstract: Sepsis is a condition characterized by organ dysfunction resulting from the systemic inflammatory response triggered by an infection. Excessive inflammation and immunosuppression are intertwined, and severe cases may even develop into multiple organ failure. Studies have shown that indoleamine 2, 3-dioxygenase 1-mediated tryptophan metabolism is involved in the occurrence and development of sepsis, and elevated plasma kynurenine levels and Kyn/Trp ratios are early indicators of sepsis development. In this paper, we provide a comprehensive summary of the role of IDO1 in the acute inflammatory phase of sepsis, late immunosuppression, and organ damage. This includes its regulation of inflammatory state, immune cell function, blood pressure, and other aspects. Additionally, we analyze preclinical studies on targeted IDO1 drugs. An in-depth understanding and study of IDO may help to understand the pathogenesis and clinical significance of sepsis and multiple organ damage from a new perspective and provide new research ideas for exploring its prevention and treatment methods.