Objective: To compare the efficacy and safety of dexmedetomidine (DEX) combined with levobupivacaine for ultrasound-guided brachial plexus block. Methods: A total of 120 patients with upper extremity surgery of the ASA I–II level were enrolled and divided into 4 groups according to random number table method, namely a control group (NS) and 3 dexmedetomidine (D1, D2, D3) groups, 30 cases in each group, both in downlink brachial plexus nerve block guided by ultrasound, injecting 0.375% left than paid 30 mL. Among them, the control group (NS) and dexmedetomidine D1 group, D2 group, D3 group were compounded with 2 mL normal saline and dexmedetomidine 50, 100, 150 μg, respectively. The pain sensation and motor block maintenance time, analgesia time, hemodynamic changes and sedation score were observed. Results: With the increase of dexmedetomidine dose, the duration of pain, motion block and analgesia were significantly prolonged (P<0.01), and the depth of sedation was also deepened (P<0.05). Conclusion: Dexmedetomidine combined with levobupivacaine can produce dose-dependent pain, prolonged motion block and clinically related sedation. Dexmedetomidine with 100 μg has a reliable and safe effect.