Objective To evaluate the efficacy of dexmedetomidine combined with oxycodone for patient-controlled intravenous analgesia (PCIA) for post spine surgery． Methods One hundred ASA I or II patients of both sexes，aged 29-63 yr，weighing 49-77 kg，undergoing elective spine surgery，were randomly divided into 4 groups(n= 25 each) using a random number table：1.0mg•kg oxycodone group (group O), 1.0mg•kg oxycodone combined with 2.5μg•kg dexmedetomidine group (group OD1), 0.8mg•kg oxycodone combined with 2.5μg•kg dexmedetomidine group (group OD2)and 0.6mg•kg oxycodone combined with 2.5μg•kg dexmedetomidine group (group OD3)，In each group, the PCIA solution contained oxycodone or oxycodone and dexmedetomidine in 200 ml of normal saline. At 15 min before the end of surgery，oxycodone 0.1 mg•kg was injected intravenously, and PCIA pump was connected simuhaneously. The PCIA pump was set up to deliver a 2 ml bolus dose with a 20-min lockout interval and background infusion at 3.5～4.5 ml•h. Oxycodone 0.05 mg•kg was injected intravenously as a rescue analgesic，and VAS was maintained≤4. The requirement for the rescue analgesic was re- corded within 48h after surgery.The number of successfully delivered doses,and the occur- rence of adverse reactions such as bradycardia, hypotension, nausea,vomiting, over-seda- tion,somnolence, pruritus, and respiratory depression were recorded. Patient’s satisfaction with analgesia was recorded at 72 h after surgery. Results No patients required the rescue analgesic or developed over-sedation, vomiting, respiratory depression and hypotension in the four groups. Compared with group O，the incidence of somnolence was significantly increased in group OD1, the incidence of nausea, somnolence, bradycardia and pruritus was decreased in OD2 and OD3 groups，and the degree of patient’s satisfaction with analgesia was increased in OD1-3 groups(P<0.05). Compared with group OD1, the incidence of nausea，somnolence，bradycardia and pruritus was significantly decreased in OD2 and OD3 groups，the degree of patient’s satisfaction with analgesia was significantly increased in group OD2 (P<0.01), and the degree of patient’s satisfaction with analgesia was decreased in group OD3(P<0.05). Compared with group OD2, no significant was found in the incidence of adverse reactions (P>0.05), and the degree of patient’s satisfaction with analgesia was decreased in group OD3 (P<0.05). The number of successfully delivered doses was larger in group OD3 than in O, OD1 and OD2 groups (P<0.05). Conclusion Dexmedetomidine 2.5μg•kg added to oxycodone 0.8mg•kg for PCIA is an effective approach for post spine surgery. It Can significantly reduce the consumption of oxycodone, decrease the incidence of adverse reactions and improve the overall satisfaction of analgesia from patients．