Objective To systematically evaluate the association between frailty and risk of postoperative delirium.Methods Systematic review of literature was conducted using eight electronic databases:PubMed,Embase,CENTRAL,Web of Science,CNKI,CBM,VIP and Wanfang Data,and prospective cohort studies about association between frailty and postoperative delirium published before March 2017 were included.Two authors independently screened the literature,extracted the data,and assessed the quality using NOS Scale,and meta-analysis was conducted by RevMan 5.3 software.Results A total of eight studies involving 846 patients were included in this review.Meta-analysis showed that:frailty was associated with higher risk of postoperative delirium [OR=3.63,95％CI (2.06,6.40),P＜0.001].Subgroup analysis showed that:①Frailty assessment tool:Fried frailty criteria and other frailty assessment were associated with increased risk of postoperative delirium[OR=5.81,95％CI(3.54,9.77),P＜0.001],[OR=1.76,95％CI(1.06,2.92),P=0.03].②Age:frailty patients aged 60～74 had increased risk of postoperative delirium [OR=5.05,95％CI (3.14,8.12),P＜0.001],but for patients aged ≥ 75,frailty wasn't associated with postoperative delirium [0R=1.73,95％CI (0.99,3.00),P=0.05].③Type of surgery:for cardiovascular and non-cardiovascular surgery patients,frailty was associated with increased risk of postoperative delirium [OR=3.40,95％CI (1.64,7.05),P＜0.001],[OR=4.95,95％CI (2.41,10.16),P＜0.001].Conclusion Frailty can increase the risk of postoperative delirium.In consideration of quantity and quality of included studies,the conclusion needs to be validated by multi-centered prospective cohort studies with large sample size.