Objective: To investigate cognitive dysfunction of type 2 diabetes patients accompanied with obstructive sleep apnea syndrome (OSAS), and to analyze its relevant characteristics. Methods: Total 115 type 2 diabetes patients were divided into OSAS group (O group, n=83) and non-OSAS group (N group, n=32); Physical examination patients (C1 group, n=64) and OSAS patients without diabetes (C2 group, n=47) served as the control group. Apnea-hypopnea index (AHI), nocturnal lowest saturation of pulse oxygen (LSPO2) and simple mental state examination scale (MMSE) were evaluated. Results: Among diabetes patients, patients with OSAS have lower glycated hemoglobin, platelet count, thrombocytocrit, MMSE score and lowest mean arterial oxygen than non-OSAS patients; cognitive dysfunction state and glycemic control of patients are related to their diabetic duration, and then along with increase of diabetic duration, glycemic control becomes poor, so that cognitive dysfunction becomes more and more obvious. Conclusion: Along with increased diabetic duration in type 2 diabetes accompanied with OSAS, glycemic control becomes poor, so that cognitive dysfunction more easily occurs. Meanwhile, coagulation function of blood system in OSAS patients with diabetes is impacted to some extent.