In recent years, frequent isocitrate dehydrogenase 1/2 (IDH1/IDH2) gene mutations were found in a variety of tumors, which specifically alter arginine residues of catalytic active site in IDH1/IDH2 and confer new enzymatic function of directly catalyzing alpha-ketoglutarate (α-KG) to R-2-hydroxyglutarate (2-HG). 2-HG could competitively inhibit α-KG-dependent enzymes and might therefore contribute to tumorigenesis. In addition, mutation status of IDH1/IDH2 is closely related to the progress and prognosis of certain tumors. Thus IDH1/IDH2 is considered to be a promising biomarker for early diagnosis and prognosis and targeted therapy. In this study, the current research on IDH1/IDH2 mutation, especially the mechanisms and clinical characteristics related to tumor, are reviewed.