O{}^6-methylguanine-DNA-methyltransferase (MGMT) is a DNA repair enzyme, which reverses the alkylation of guanine O{}^6 through directtransfer of the methyl group, maintains the gene stability and avoids tumor occurrence. Studies have shown that MGMT gene methylation, polymorphism and protein expression are involved in the process of various tumor development, such as colon cancer, gastric carcinoma, etc. MGMT gene promotes methylation, protein expression and enzyme activity from various tissues, which resultsin different effects on the prognosis of patients. MGMT promoter methylation is a positive factor for the prognosis of Glioblastoma (GBM), which can prolong overall survival and progression-free survival, reduce the resistance of tumor cells to temozolomide treatment, and improve the prognosis. The treatment of tumors based on MGMT focuses on three aspects: targeting MGMT to increase the sensitivity of alkylated drug therapy in tumors, immunotherapy combined with alkylated agents on tumor treatment, and treatment for patients with MGMT promoter non-methylation. Similarly, a number of studies have targeted MGMT to reduce alkylated agent resistance in other systems. Although numerous studies on MGMT in tumors have been reported, there are problems that need to be solved, such as selection and consensus of MGMT promoter methylation detection methods (CpG detection sites, cut-off value) and the treatment of MGMT non-methylated GBM patients, especially elderly patients. In this review, we describe the regulation of MGMT expression and its role inchemotherapy, especially in gliomas. Further studies exploring new methods targeting MGMT with better curative effect and less toxicity are advocated. We anticipate that these developments will be progressive and sufficiently used for clinical application.