Introduction: To assess the effects of aquatic exercise in postmenopausal women with knee osteoarthritis using an up-to-date meta-analysis. Evidence acquisition: PubMed, Cochrane Library, Embase, Scopus, Web of Science, Google Scholar, the China National Knowledge Infrastructure (CNKI), the Chinese Biomedical Database (CBM), VIP and Wanfang database were searched systematically for randomized controlled trials (RCTs) published until July 2018. The RCTs included comparing the efficacy of aquatic exercise vs. control in postmenopausal women with knee osteoarthritis, the primary outcomes were assessed by the Western Ontario McMaster University Osteoarthritis Index (WOMAC) and the Knee injury and Osteoarthritis Outcome Score (KOOS). Evidence synthesis: Six RCTs comprising 432 participants. This meta-analysis revealed that aquatic exercise could significantly relieve the symptom of postmenopausal women with knee osteoarthritis. But there was no significant difference between aquatic exercise program and control group for the improvement of pain, stiffness, function outcomes, sport, activities of daily living and quality of life. Conclusions: Contrary to prior reviews, our analysis demonstrated that aquatic exercise has no positive impact on pain physical function, stiffness, activities of daily living, sport and quality of life in elderly women with knee osteoarthritis. However, aquatic exercise could improve the symptoms of knee osteoarthritis. Further investigation is needed because of limited available data.