Abstract: Objective To access the changes of sleep spindles in patients with obstructive sleep apnea （OSA）. Methods This is an observational, cross-sectional study consecutively recruited out patients at the sleep center of Guangdong Provincial People's Hospital, China between July 2019 and April 2021. Patients were aged 18~65 years and underwent overnight polysomnography （PSG） by Phillips Alice 6 LDXS. Exclusion criteria were any sleep disorder or mental health issues other than OSA including current treatment for sleep apnea, insomnia and depression. Subjects who reported taking sleep aids were also exclude. The participants were divided into four groups according to their apnea-hypopnea index （AHI）: normal （AHI<5）, mild （5≤AHI<15）, moderate （15≤AHI<30）, and severe （AHI≥30）. One-way ANOVA or nonparametric test was used for comparison between groups. Associations between sleep spindles and other parameters were analyzed with a general linear model. Results 252 adults were included （33 in normal group, 58 had mild OSA, 60 had moderate OSA and 101 had severe OSA） with the mean age 44.8±11.7 years, mean body mass index （BMI） 25.5±3.8 kg/m² and mean AHI 28.6±23.2/h. The numbers of sleep spindles in N2 was 411.0 （151.5, 1 569.5） in the normal, 315.5 （150.0, 667.8） in the mild, 251.0 （96.0,680.8） in the moderate, 224.0 （75.0, 567.5） in the severe, with significance between group difference （P=0.002）. The destiny of sleep spindles in N2 was 2.6（0.7, 7.4） in the normal, 1.6 （0.7, 2.9） in the mild, 1.2 （0.4, 3.7） in the moderate and 0.9 （0.3, 2.5） in the severe, with significance between group difference （P<0.001）. There was a trend that the destiny of sleep spindles in N2 decreased with the increase of AHI （P=0.028） and BMI （P=0.012）. Conclusions The number and destiny of sleep spindles in N2 had a significant decrease in severe OSA patients and the destiny of sleep spindles in N2 decreased with the increase of AHI and BMI.