Objective To systematically review qualitative researches on ICU diary use by relatives of ICU patients,and provide evidence for humanistic care measures for relatives of critically ill patients. Methods The following databases including PubMed，Web of Science，Embase，Science Direct，CNKI，Wanfang Data and VIP,and the website of AACN were searched for publications indexed from inception to May 2019 to collect qualitative studies on relatives′ experiences with intensive care unit diaries. The JBI Critical Appraisal Tool for qualitative studies （2017 edition） was used to evaluate the quality of included studies. Meta-synthesis was applied to integrate the results. Results Totally 7 studies containing 29 findings were included. Then 10 new categories were generated and finally 3 synthesized results were obtained：relatives′ own feelings(information and emotional needs being met, though some people showed opposition),interaction between relatives and patients(maintaining communication, and feeling pressure), relatives′ attitudes towards medical staff (humanistic care, and trust). Conclusion ICU diary can effectively meet relatives′ needs for information and provide emotional support. Effective interventions suited to China′s national conditions shall continue to be explored, and humanistic care needs a boost in the future.