Objective To investigate the influencing factors of patients' sleep quality before operation. Methods A total of 886 patients scheduled for elective surgery from June 1， 2017 to October 1， 2017 were selected by stratified random sampling method. The general data of the patients was collected and a questionnaire survey was conducted on the day before operation， including the Medical Outcomes Study Sleep Scale（ MOS-SS）， the self-designed sleep-related factors questionnaire， Visual Analogue Scale（ VAS）， Hospital Anxiety and Depression Scale（ HADS）. Results The sleep problems index（ SPI） and the incidence of sleep disorder one month before operation were 35.8（ 28.3， 45.3） and 63.1%（ 559/886） respectively. Those indicators one week before operation were 37.7（ 30.2，47.2） and 67.7%（ 600/886） respectively. The differences were statistically significant（ Z=-5.367，χ2=60.749； P ＜ 0.01）. It is indicated in the self-designed sleeprelated factors questionnaire that the factors of noise， the sleep environment changes， the discomfort caused by illness and the roommates influencing sleep quality comprised 34.1%， 25.4%， 23.8% and 14.7% respectively. Multivariate Logistic regression analysis showed that occupation， religion， anxiety and depression affected the quality of sleep in one month before surgery， and gender， pain level during activity， anxiety， depression and the department of surgery affected the quality of sleep in one week before surgery. Conclusions Preoperative sleep disorder is very prevalent and related to multiple factors.