ObjectiveTo explore the relationship between metformin use and the risk and prognosis of esophageal cancer in patients with diabetes.MethodsThe PubMed, Web of Science, EMbase, VIP, WanFang and CNKI databases were searched by computer to identify relevant studies from inception to August 21, 2021. Newcastle-Ottawa scale (NOS) was used to evaluate research quality. The STATA 12.0 software was used to conduct the statistical analysis.ResultsA total of 14 studies involving 5 605 218 participants were included finally. NOS of all researches were≥6 points. The pooled results indicated that metformin use could decrease the risk of esophageal cancer in diabetics (OR=0.84, 95%CI 0.71-1.00, P=0.045), and could also prolong the overall survival of diabetics with esophageal cancer (HR=0.89, 95%CI 0.80-0.99, P=0.025).ConclusionMetformin use can not only decrease the risk of esophageal cancer in patients with diabetes, but also improve the prognosis of diabetics with esophageal cancer significantly. However, more prospective high-quality studies are still needed to verify the conclusion.