Objective: To investigate the differences in ischemic changes on ambulatory electrocardiography and circadian rhythm of heart rate variability (HRV) in patients with different degrees of sleep disorders. Methods: A total of 86 patients with sleep disorders were enrolled and divided into mild group (n=29), moderate group (n=30), and severe group (n=27) according to the Pittsburgh sleep quality index (PSQI). All patients underwent 24-hour ambulatory electrocardiography. The detection rates of abnormal electrocardiogram, myocardial ischemia indices, and HRV indices during awake and sleep periods were compared among the three groups. Results: The detection rates of sinus bradycardia and ST-T changes in the severe group were significantly higher than those in the mild group (P < 0.05). The myocardial ischemia indices during both awake and sleep periods were significantly higher in the severe group than in the moderate and mild groups (P < 0.05). SDNN, SDANN, rMSSD, pNN50, TP, and HF were significantly lower, while LF and LF/HF were significantly higher in the severe group than in the other two groups (P < 0.05). The mild group showed normal circadian rhythm of HRV, the moderate group showed weakened rhythm, and the severe group showed disappearance of circadian rhythm. Conclusion: The more severe the sleep disorder, the more obvious the ischemic changes and the more significant the HRV circadian rhythm abnormality. Ambulatory electrocardiography is helpful for cardiovascular risk assessment in patients with sleep disorders.