Abstract: Objective To evaluate the change characteristics of entropy in monitoring sedation depth of dexmedetomidine when applied in pre – anesthesia induction of patients with chronic renal failure and secondary hyperparathyroidism that were planning to do parathyroidectomy and autotransplantation. Methods Nine ASA physical status Ⅱ~Ⅲ patients with chronic renal failure, aged 18~65 yr, with BMI of 18~25 kg/m2, scheduled for parathyroidectomy were included into Group E, and nine ASA physical status Ⅰ~Ⅱ patients with no systemic disease were included into Group C. Dexmedetomidine injection（drug concentration was 4μg/ml） 0.9mlkg/h was infused intravenously in both groups for 10 minutes before anesthesia induction. Recorded the value of RE and SE before infusion (T0), and 1 min (T1), 5min (T2), 7 min (T3), 11 min (T4) since the infusion started, then calculated D-value of RE-SE. Results Compared with T0, both of RE and SE in Group E was significantly decreased at T4; RE and SE in Group E was significantly lower than Group C at T4, likewise RE-SE at T3. Conclusion To compared with normal patients，entropy was significantly lower in monitoring sedation depth of dexmedetomidine when applied in pre – anesthesia induction of patients with chronic renal failure and secondary hyperparathyroidism.