Objective To evaluate the effect of ropivacaine combined with low-dose naloxone or sufentanilropivacaine mixture on brachial plexus block carried under the guidance of ultrasound.Methods A total of 100 patients of our hospital undergoing upper limb surgery was randomly divided into four groups with 25 patients in each group.Four groups are patients receiving 20 mL of 0.375％ mesylate ropivacaine (Group D),20 mL of 0.375％ mesylate ropivacaine + 10 μg sufentanil (Group S),20 mL of 0.375％ mesylate ropivacaine + 100 ng naloxone (Group N) and 20 mL of 0.375％ mesylate ropivacaine + 10 μg sufentanil +100 ng naloxone (Group N+S).All patients underwent interscalene brachial plexus block under ultrasound guidance.The sensory block,motor block and other adverse reactions were observed and recorded at 5min,6,12,18,24 h.Results The sensory and motor block time of group D was (435.5 ± 77.9) min and (350.2 ± 69.8) min,group S (831.7 ± 52.0)min and (675.8 ± 48.1)min,group N (933.0 ± 117.1) min and (499.0 ± 40.5) min,group N+S (919.3 ± 59.0) min and (534.8 ± 56.6)min.The sensory block time of group N and group N + S were significantly longer than that of group D and S (P ＜0.05).The sensory and motor block time of group D were obviously shorter than that of other groups (P ＜ 0.05).There were no significant difference in the onset time of sensory and motor block in all groups.Conclusion Low dose of naloxone combined with ropivacaine or sufentanil-ropivacaine mixture can increase the duration of sensory block on brachial plexus.