Lactic acid, a widespread metabolite in the tumor microenvironment, is mainly produced by tumor cells that undergo aerobic glycolysis. Lactic acid is closely related to the occurrence and development of tumor. It not only serves as a substrate to supply energy to tumor cells, but also acts as a signaling molecule to activate multiple pathways to promote invasive and metastasis, angiogenesis and immune escape of tumor cells. In-depth research on the mechanism of action of lactic acid in the occurrence and development of tumor and related therapeutic progress will help to find drug targets for treatment of tumor and improve prognosis of patients.