Cohesin plays an important role in multiple physiological processes including DNA repair, cell cycle and gene expression regulation. Studies showed that Cohesin defect is closely associated with tumorigenesis. STAG2, a core protein of cohesion, ubiquitously expressed in normal cells. In recent years, it has widely been paid attention to role of deletion or mutation of STAG2 in occurrence of many tumors. Further research on the effects and molecular mechanisms of STAG2 gene deletion or mutation in tumor development can provide new ideas and new targets for diagnosis and treatment of tumor. This paper reviews the potential function of STAG2 in human malignancies.