Previous studies have reported that microRNA-21 (mRNA-21) has an effect on the prognosis of pancreatic cancer. However, the conclusion is still unclear. Therefore, this study will try to explore the effect of high expression of mRNA-21 on the prognosis of pancreatic cancer.Retrieved the database, including the China National Knowledge Infrastructure (CNKI), Chinese Biomedical literature Database (CBM), Chinese Scientific and Journal Database (VIP), Wan Fang database, PubMed, and EMBASE. Hazard ratios (HRs) and its 95% confidence intervals (CIs) to assess the prognostic effect of miRNA-21 on overall survival (OS) and disease-free survival (DFS). RevMan 5.3 and STATA 16.0 software were used to perform the meta-analysis.This study will comprehensively review and evaluate the available evidence of high expression of miRNA-21 on the prognosis of patients with pancreatic cancer.Our findings will show the effect of high expression of miRNA-21 on the prognosis of patients with pancreatic cancer. Such studies may find a new prognostic marker for patients with pancreatic cancer and help clinicians and health professionals make clinical decisions.The private information from individuals will not publish. This systematic review also will not involve endangering participant rights. Ethical approval is not available. The results may be published in a peer- reviewed journal or disseminated in relevant conferences.