Objective To evaluate the effects on mechanical ventilation in ICU patients with dexmedetomidine merely and combined with dezocine, fentanyl, respectively.Methods Fifty-seven patients with mechanical ventilation in ICU were collected during Jun till Dec in 2016, 35 males and 22 females, aged 18-75 years, and classified into three groups with random number table method, among whom there were 17 patients treated with dexmedetomidine, 20 patients treated with dexmedetomidine combined with dezocine and 20 with dexmedetomidine plus fentanyl, the general condition, pain score, MAP and HR were compared before and after the treatment, ideal treatment time and mechanical ventilation time were also compared among the different groups.Results There were no statistical differences in the general condition, CPOT score, MAP and HR at different points and mechanical ventilation time.Whereas, the time of ideal sedation and analgesia was significantly faster in group C than that of groups A and B (P<0.05).Conclusion Dexmedetomidine combined with dezocine can reach the ideal analgesic effect more rapidly than dexmedetomidine solely or combined with fentanyl.