Objective: The purpose of this study was to investigate the abnormal coagulation function of OSA patients with different degrees of severity, and to lay a foundation for further elucidating the relationship between OSA and cardiovascular and cerebrovascular diseases.Methods: According to the presence and severity of OSA, patients were divided into mild OSA group, moderate OSA group, severe OSA group and control group. All patients were tested by PSG, blood routine, blood coagulation routine and thromboelastography.Results: there was no significant difference in PLT, PCT, MPV and APTT between the four groups (P > 0.05).PDW of mild to moderate OSA group was significantly different from that of control group (P < 0.01).There were significant differences in PT and PT-INR between moderate and severe OSA group and control group (P < 0.01).There were significant differences in R, K, and MA between mild, moderate and severe OSA group and control group, respectively.R and MA in moderate and severe OSA group were significantly different from those in mild OSA group (P < 0.01).There was a significant difference in K between severe and mild OSA groups (P < 0.01).Conclusion: This study revealed that OSA patients had abnormal coagulation function. With the increase of AHI, the hypercoagulability status was more significant, which may be related to the increased risk of OSA for cardiovascular and cerebrovascular diseases.Compared with routine blood test and routine blood coagulation,thromboelastography is more sensitive and has more comprehensive clinical significance.