Objective To systematically review the correlation between obstructive sleep apnea syndrome (OSAS) and the incidence of carotid atherosclerosis. Methods PubMed, EMbase, CNKI, WanFang Data, CBM, and VIP databases were electronically searched to collect studies on the correlation between OSAS and carotid atherosclerosis and carotid intima-media thickness (CIMT) from inception to August 2021. Two reviewers independently screened literature, extracted data, and assessed the risk of bias of the included studies. Meta-analysis was then performed using Stata 16.0 software and RevMan 5.3 software. Results A total of 32 studies, including 2 915 patients were included. The results of the meta-analysis showed a higher incidence of carotid atherosclerotic plaque in OSAS patients than in the control group (OR=5.56, 95%CI 0.27 to 8.38, P<0.000 01); subgroup analysis revealed that, compared with the control group, patients who were male (OR=5.38, 95%CI 2.79 to 10.38, P<0.000 01) or had mild-to-moderate OSAS (OR=3.9, 95%CI 1.66 to 9.15, P=0.002) or severe OSAS (OR=19.86, 95%CI 6.49 to 60.82, P<0.000 01) had a higher risk of carotid atherosclerosis. The CIMT of the OSAS group was significantly higher than that of the control group (SMD=1.24, 95%CI 0.97 to 1.51, P<0.000 01). There was a positive correlation between the apnea hypopnea index (AHI) and CIMT in OSAS patients (r=0.52, 95%CI 0.44 to 0.60, <0.000 1), and the CIMT increased with OSAS severity. Conclusion OSAS is associated with a high incidence of carotid atherosclerotic plaque that is highly correlated with CIMT, which increases with an increase in the AHI. These findings are required to be verified in prospective high-quality studies to overcome the limitations of quantity and quality of studies included in this systematic review.