Objective To investigate the knowledge，attitude and behavior of ICU nurses on hypoactive delirium and analyze its influencing factors. Methods A total of 780 ICU nurses were selected from 38 districts and counties in Chongqing by convenience sampling method，and a cross-sectional survey was conducted using the questionnaire of hypoactive delirium knowledge，attitude and behavior of ICU nurses. Results ICU nurses had poor knowledge of hypoactive delirium，and were active in early identification and nursing of patients with hypoactive delirium，and it was needed to improve early treatment and screening of hypoactive delirium. Through multiple linear regression analysis，different years of working experience in ICU（t=-3.453，P=0.001），caring for patients with delirium（t=2.795，P=0.005），attending training on ICU hypoactive delirium（t=3.712，P<0.001） had impact on the knowledge score of ICU nurses，different professional titles（t=2.941，P=0.003） had impact on the attitude score of ICU nurses，attending training on ICU hypoactive delirium（t=6.458，P<0.001）had an impact on the behavior score of ICU nurses. Conclusion ICU nurses in different level of hospitals have poor knowledge of hypoactive delirium，it is urgent to improve regular delirium screening and early management of patients. It is necessary to develop standardized assessment and nursing programs for hypoactive delirium and improve the nursing quality of hypoactive delirium.