Objective This study was designed to compare the sedative effects of three intranasal dexmedetomidine (Dex) doses for premedication in children undergoing adenotonsillectomy. Methods One hundred and ninety‑two children undergoing elective adenotonsillectomy were randomly divided into Dex 2 µg/kg group (group A), Dex 3 µg/kg group (group B) and Dex 4 µg/kg group (group C), n=64 each. After entering the operation waiting area, the children in different groups received intranasal Dex 2, 3 µg/kg or 4 µg/kg respectively, the sedation status was assessed after administration. Once the children achieved satisfactory sedation state, they were transferred to the operating room for anesthesia and surgery. Researchers recorded onset time of sedation, recovery time and vital signs of children before and after administration and recovery. Then they calculated the emotional satisfaction rate of kids when they were separated with parents, the satisfaction rate of venipuncture after admission, the incidence of agitation and pain after awaking and postoperative adverse reactions. Results Compared with group A, the onset time of sedation was significantly shortened in group B and group C， the difference was statistically significant (P<0.05). Compared with group A and group B, the postoperative recovery time of group C was significantly prolonged (P<0.05). After administration, the pulse oxygen saturation (SpO2) and heart rate in the three groups was declined (P<0.05), the heart rate was declined in group C (P<0.05). The heart rate and SpO2 in group C were statistically lower than the values in group A and group B at each time point (P<0.05). The emotional satisfaction rate at separating time of the kids in the three groups were all over 90%， there was no significant difference between the three groups (P>0.05). The satisfaction rates of venipuncture in group B and group C were higher than that in group A, but the difference was not statistically significant (P>0.05). The incidences of agitation and pain in the three groups were lower than the incidences after awakening, but the differences were not statistically significant (P>0.05). In group C, bradycardia occurred in 3 children after anesthesia induction and were relieved after given 0.01 mg/kg of atropine; which did not happen again during the operation. Conclusions Intranasal Dex 3 µg/kg before adenotonsillectomy can effectively alleviate preoperative anxiety and have a quicker onset time of sedation. The satisfaction rates of children's separating emotion and venipuncture are high. At the same time, it has less effect on children's vital signs and the recovery time and quality.