Abstract: Objective: To explore the risk factors of ICU delirium in adult patients to provide the basis for early clinical identification of delirium. Methods: We searched databases including The Cochrane Library, PubMed, Embase, Web of Science, CNKI, WanFang Data, VIP and CBM from inception to April 2017, to collect the risk factors of ICU delirium in adult patients at home and abroad. RevMan 5.3 software were used for Meta-analysis. Results: Twenty-six studies were included, the cumulative cases were 2 267 delirium cases and 10 746 controls. The pooling effect sizes which include odds ratio (OR) values and weight mean difference (WMD) were age >65 years (OR=2.19), smoking (OR=1.22), COPD (OR=2.08), sedatives (OR=8.27), mechanical ventilation (OR=3.46), sepsis (OR=8.88), APACHE II score (WMD=3.77), stroke (OR=2.20), renal dysfunction (OR=1.96) and physical restraint (OR=9.99), respectively. Conclusion: According to the present evidence, the risk factors of delirium in ICU patients are age >65 years, smoking, COPD, sedatives, mechanical ventilation, sepsis, APACHE II score, stroke, renal dysfunction and physical restraint.