Background: Meta-analysis results of observational studies show that metformin can prolong progression-free survival and overall survival in cancer patients However, these studies do not strictly distinguish whether patients have type 2 diabetes or not Therefore, whether metformin adjuvant chemotherapy can improve the prognosis of non-diabetic tumor patients still needs further verification Methods: Embase、Pubmed and The Cochrane library was systematically searched for metformin and tumor subject words and free words. Extract PFS,OS and other related data according to the eligibility criteria. The pooled data were analysed by meta-analysis using Revman 5.4 to assess the efficacy and safety of metformin application. Results: A total of 3228 articles were retrieved from the database. After screening, a total of 13 studies and 1255 patients were included in meta-analysis. All included studies were randomized controlled trials. Metformin combined with adjuvant chemotherapy did not improve progression-free survival (HR=0. 01, 95CI-0. 24-0.26) ，overall survival (HR=-0. 03, 95% CI-0. 32-0.26) and not increase the objective response rate of patients. There was no significant difference in the occurrence of grade 3-4 adverse reactions compared with placebo Conclusions: Our findings suggest that chemotherapy combined with metformin may not be beneficial in patients with non-diabetic tumors, especially in patients with non-small cell lung cancer, Therefore more high-quality randomized controlled trials are needed to verify the positive effect of metformin in chemotherapy in non-diabetic tumors patients.