Abstract: Metformin is one of the most widely used oral hypoglycemic drugs.Multiple studies have shown that metformin exhibits pleiotropic effects other than hypoglycemic effects, such as cardioprotective effects, improvements in the blood lipid profile, and possibly anticancer effects.Epidemiological data also show a reduction in cancer morbidity and mortality in patients treated with metformin.As research has progressed, metformin has attracted more attention as a potential and attractive adjuvant anticancer drug.Clinical trials on the mechanism and efficacy of metformin have been conducted in different cancers.With publication of the results of more clinical trials, the effects of metformin combined with chemotherapy, radiotherapy, molecular targeted drugs, or immunotherapy, and its effects on certain metabolic molecules will be verified.This could provide more definitive evidence of the benefits of metformin in combination with cancer therapy and facilitate the clinical application of metformin as an adjunctive anticancer agent.