Object We explored the relationship between obstructive sleep apnea (OSA) and depressive disorder.Method 88 patients suffered from OSA were divided into mild, moderate and severe according to the apnea-hypopnea index (AHI) and the lowest oxygen saturation at night.All the patients accepted the Zung self rating depression scale (SDS) test, including 20 subjects to analysis the situation of the depressive disorder.The standard score is that the SDS score multiplied by 1.25.If the standard scores ≥50 the patients should have the depressive disorder.We compared the morbidity of depressive disorder in every group, then discussed the relationship between OSA and depressive disorder, moreover, we discussed the relevant factors.Results 47.73% OSA patients developed the depressive disorder,significantly higher than the control group.The morbidity of depressive disorder in mild, moderate and severe group respectively are 11.9%、 38.1%、 50.0%.42 patients who have OSA and depressive disorder, the SDS scores are higher with the increasing of BIM, AHI, and SaO2min at night.Conclusion 1.There is relationship between OSA and depressive disorder.In the OSA patients, the incidence rate of depressive disorder is increasing with the severe degree of OSA.2.When the patients have the OSA and depressive disorder,the degree of the depressive disorder is positive correlative with BMI, AHI,ESS and is negative correlative with SaO2min at night.3.The OSA patients should pay attention to develop the depressive disorder, and the survey of depressive disorder should be carried out in the OSA patients regularly, which is good for the clinical diagnosis and treatment.