Objective To evaluate the sedative and analgesic efficacy and adverse effect of dexmedetomidine versus propofol on the postoperative patients in intensive care unit (ICU). Methods The relevant randomized controlled trials (RCTs) were searched in The Cochrane Library, MEDLINE, PubMed, SCI, SpringerLinker, ScinceDirect, CNKI, VIP, WanFang Data and CBM from the date of their establishment to November 2011. The quality of the included studies was evaluated after the data were extracted by two reviewers independently, and then the meta-analysis was performed by using RevMan 5.1. Results Ten RCTs involoving 793 cases were included. The qualitative analysis results showed: within a certain range of dosage as dexmedetomidine: 0.2-2.5 μg/(kg·h), and propofol: 0.8-4 mg/(kg·h), dexmedetomidine was similar to propofol in sedative effect, but dexmedetomidine group needed smaller dosage of supplemental analgesics during the period of sedative therapy. The results of meta-analysis showed: the percentage of patients needing supplemental analgesics in dexmedetomidine group was less than that in propofol group during the period of sedative therapy (OR=0.24, 95%CI 0.08 to 0.68, P=0.008). Compared with the propofol group, the duration of ICU stay was significantly shorter in the dexmedetomidine group (WMD= –1.10, 95%CI –1.88 to –0.32, P=0.006), but the mechanical ventilated time was comparable between the two groups (WMD=0.89, 95%CI –1.15 to 2.93, P=0.39); the incidence of adverse effects had no significant difference between two groups (bradycardia: OR=3.57, 95%CI 0.86 to 14.75, P=0.08; hypotension: OR=1.00, 95%CI 0.30 to 3.32, P=1.00); respiratory depression seemed to be more frequently in propofol group, which however needed further study. Mortalities were similar in both groups after the sedative therapy (OR=1.03, 95%CI 0.54 to 1.99, P=0.92). Conclusion Within an exact range of dosage, dexmedetomidine is comparable with propofol in sedative effect. Besides, it has analgesic effect, fewer adverse effects and fewer occurrences of respiratory depression, and it can save the extra dosage of analgesics and shorten ICU stay. Still, more larger-sample, multi-center RCTs are needed to provide more evidence to support this outcome.