Abstract: In recent years, colorectal cancer (CRC) has become one of the most common malignant tumors with moderate morbidity and mortality rates. Epidemiological studies proved the increasing trend of CRC incidence in China. Metformin is widely used in clinics as an oral antidiabetic drug. Clinical and experimental studies have determined its role on the inhibition of colorectal tumor prolifera -tion. The mechanisms mainly include the inhibition of the mechanistic target of rapamycin signaling pathways, limitation of the growth of cells lacking P 53, inhibition of the function of signal transducer and activator of transcription 3, and reduction of fatty acid synthe -sis. Other mechanisms involve the inhibition of cell cycle, induction of autophagy and apoptosis, reduction of the functions of insulin and the insulin receptor, and cooperative interaction with chemotherapy drugs. However, some related studies did not show obvious inhibition on CRC progression by metformin. Therefore, as a potential antitumor and adjuvant chemotherapy drug for CRC, further studies on the effects of metformin should be conducted to acquire more clinical evidence.