Abstract: Objective To compare the clinical characteristics and prevalence of chronic complications in type 2 diabetes mellitus (T2DM) patients with various degrees of obstructive sleep apnea syndrome (OSAS). Methods A total of 170 patients with T2DM and OSAS were enrolled in this study. These participants were divided into three groups with low, medium and high apnea-hypopnea index (AHI), respectively. The demographic characteristics, biochemical indicators and chronic complications of the patients in the three groups were compared. Multivariate Logistic regression analysis was performed to determine the associations between chronic complications and OSAS. Results The patients with severe OSAS had higher waist circumference (P=0.045), higher BMI (P=0.069), higher prevalence of diabetic peripheral neuropathy (DPN), and higher prevalence of diabetic retinopathy (DR) than the patients with mild-moderate OSAS. Similar levels of macrovascular complications were found in the three groups (P>0.05). The logistic regression analyses showed that DPN (OR=1.024, 95%CI 1.002-1.046) and chronic kidney disease (OR=1.026, 95%CI 1.004-1.049) were independent predictors of AHI, adjusting for the lowest oxygen saturation, gender, age, diabetic duration, family history of diabetes, BMI, and HbA1c. Other microvascular and macrovascular complications were not predictors of AHI. Conclusion Patients with T2DM and severe OSAS have a higher risk of DPN and DR. Particular attention should be paid to T2DM patients with severe OSAS to prevent complications.