Objective To investigate the efficacy and safety of different doses of dexmedetomidine（DEX） administered in the laparoscopic gynecological surgery. Methods Eighty patients ASA grades Ⅰ or Ⅱ, scheduled for elective laparoscopic gynecological surgery under general anesthesia were randomly divided into four groups, 20 patients in each group: group A (Control group, 10ml normal saline), group B (0.25μg/kg DEX), group C (0.5μg/kg DEX ), group D (1.0μg/kg DEX). Before induction of anesthesia, patients were administered intravenously 10ml saline or different doses of dexmedetomidine (diluted with saline to 10ml) in 10minutes with syringe pump respectively. Systolic blood pressure（SBP）, diastolic blood pressure（DBP）, heart rate（HR） and bispectral index（BIS） value were recorded 15min after entering operating room(T0), after given dexmedetomidine infusion(T1)，immediately before and after tracheal intubation(T2-T3), after pneumoperitoneu (T4), after skin incision (T5), at the end of surgery (T6) and extubation(T7), meanwhile the amount of propofol and remifentanil, recovery time, extubation time and adverse reactions were also recorded. Results In group A, B, SBP, DBP and HR at each time after intubation was significantly higher than that before induction, while in group C, D there were no significant changes in those parameters among the different time points. SBP, DBP and HR after intubation in group C and group D were lower than that at the same time point in group A and group B. At time point T1, HR were significantly decreased and SBP, DBP increased compared with that at time point T0. Values of BIS were significantly lower at time point T1 in group B, C and D (P<0.05) compared with that at time point T0. Values of BIS at time point T1 in group B, C were significantly higher (P<0.05) compared with that in group D. There were significant differences in the doses of propofol administered in four groups (P<0.05), the doses were（834±109, 725±94, 615±110, 563±97）mg in group A, group B, group C and group D respectively. The doses of remifentanil used in four groups were respectively （562±53, 497±32, 431±41, 442±37）µg. Recovery time and extubation time of the patients among 4 group were no statistically significant different (P >0.05). The dosage of epherine and atropine administered in group D increased obviously (P<0.05) and higher incidence of chill, dysphoria and cough was observed in group A and group B(P<0.05). Conclusions：Before induction of anesthesia, administration of different doses of DEX have significant sedative effects on patients, can reduce the dose of propofol and remifentanil and may reduce the adverse reactions. Cardiovascular parameter changes was more stable within different stage of surgery in the group which 0.5μg／kg DEX was administered before anesthesia.