Objective：To evaluation the efficiency of different dose of dexmedetomide combined with butorphano in Patient-controlled intravenous analgesia after total hip replacement in the elderly. Methods：The study involved 60 cases scheduled for total hip replacement in our hospital from June 2018 to June 2019，sixty patients of ASA Ⅰ or Ⅱ aged from 60~75 were randomly devided into three groups（C、D1 and D2 group），20 cases in each group. All of them performed Patient-controlled intravenous analgesia after operation. In C group，PCIA solution contained butorphano 0.15 mg·kg-1；In D1 group，PCIA solution contained butorphano 0.15 mg·kg-1+dexmedetomide 1.5 μg·kg-1；In D2 group，PCIA solution contained butorphano 0.15 mg·kg-1+dexmedetomide 2.0 μg·kg-1，which in all groups were diluted with normal saline to 100 ml.The VAS pain score ，Ramsay sedation score，blood pressure，heart rate and adverse reactions were evaluated at 4，8，24，36，and 48 hours after operation. Results：Compared with C group，the VAS pain score，Ramsay sedation score of D1 and D2 is better than that of C group （P<0.05），the difference of VAS pain score ，Ramsay sedation score were not statistically significant（P>0.05）；Blood pressure （systolic blood pressure，diastolic blood pressure） and heart rate of each group at different time points were lower than those of C group（P<0.05）； The incidence of nausea，vomiting and dizziness was significantly higher in C group （P<0.05），the incidence of hypotension and bradycardia was significantly higher in D2 group（P<0.05）； The PCIA pressing times of group C was significiently higher than D1 and D2 group（P<0.05）. Conclusion：butorphano 0.15 mg·kg-1 and dexmedetomide 1.5 μg·kg-1 used for PCIA after total hip replacement in elderly is significant and fewer side effects.