Objective To summarize the relevant evidence of airway clearance in adult ICU patients and to provide evidence-based reference for nursing staff to implement airway clearance technique. Methods The literature on airway clearance in ICU patients was systematically searched from relevant guideline websites, evidence-based databases, websites of relevant professional society/organizations and original literature databases, and the search period was from January 1, 2012 to March 31, 2022. Results A total of 19 articles met eligibility criteria, including one evidence summary, two guidelines, three systematic reviews, five randomized controlled trials, and eight expert consensus/opinions statements. A total of 35 pieces of best evidence were formed, including seven aspects: basic requirements of airway clearance, target population, assessment, selection of airway clearance techniques, condition observation and monitoring, notice, and patient education. Conclusion The best evidence of airway clearance in adult ICU patients summarized in this study is comprehensive and practical. Nursing staff should formulate targeted and individualized airway clearance programs according to the actual situation of patients, and promote the implementation of evidence into clinical practice, thus to improve clinical outcome and prognosis of ICU patients.