Abstract: Objective: To study the effect of midazolam through different ways of administration.Methods: Forty ASA Ⅰ to Ⅱ patients scheduled for elective surgery were enrolled in this study.They were randomly divided into four groups with 10 cases in each group.They were intravenous group(V group),intramuscular group(M group),intranasal group(N group) and subligual group(S group).Each group was given midazolam 50 μg/kg for premedication by different ways of administration.The depth of sedation was monitored by BIS and modified by OAA/S sedation score,VAS score and amnesia.Results: The OAA/S score:70% of the patients in two groups(V,M) became unconscious.However,only 30% of the patients in the other groups(N,S) became unconscious.The BIS index decreased to 84.3±2.17 in V group,89.9±1.23 in M group,91.1±0.84 in N group and 91.3±0.61 in S group.The BIS index in group(V,M,N,S) decreased slightly 5 min,25 min,35 min and 35 min after administration.There were significant changes in the VAS score after giving premedication in V,M and N group(P<0.05 to P<0.01).The percentage of amnesia changed significant(P<0.01).Conclusions: The effects of sedation and amnesia of midazolam administered in a dose of 50 μg/kg are better in V and M groups than in N and S groups.