Abstract: ob＜x＞ject To observe the effects of different doses of dexmedetomidine on negative postoperative behavioural changes of children undergoing eyelid surgery under general anesthesia. Methods One hundred and ninty-two children of both genders, ASA ? or ???? aged 3-7 years, weighed 12-40 kg, undergoing eyelid surgery, were equally assigned into four groups (n=48) using a random number table: control group (group C), dexmedetomidine 1 ug/kg group (group D1), dexmedetomidine 2 ug/kg group (group D2) and dexmedetomidine 3 ug/kg group (group D3). Thirty minutes before anesthesia induction, all the children were received nasal spray normal saline 0.02 ml/kg (group C), dexmedetomidine 1ug/kg (group D1), dexmedetomidine 2 ug/kg (group D2), dexmedetomidine 3 ug/kg (group D3), respectively. The preoperative sedation score, emotional score of separation from their parents, mask acceptance score, the number of restless cases in the PACU, restless score, extubation and recovery time, PACU residence time after extubation, perioperative adverse events were recorded. A questionnaire and telephone follow-up were carried out on the parents at 1, 7 and 30 d postoperatively to obtain the negative postoperative behavioural changes (NPOBCS). Results Compared with group C, the incidence of adverse behavior change was significantly lower in group D1, D2 and D3 at day 1, 7 and 30 after surgery (P < 0.05). Compared with D1 group, the incidence of adverse behavior changes 7 days after operation in D2 and D3 groups was significantly reduced (P < 0.05). 1 and 7 days after surgery, the incidence of separation anxiety and sleep anxiety in group D was significantly lower than that in group C (P < 0.05). There was no significant difference in the incidence of other behavioral changes (P > 0.05). Compared with group C, Ramsay sedation score, separation emotion score, mask acceptance score and postoperative agitation score of children in group D1, D2 and D3 were significantly reduced (P<0.05). The wake time of children in D3 group was significantly longer than that of the other 3 groups (P < 0.05), and there was no significant difference in extubation time, bradycardia, or laryngospasm among the 4 groups (P > 0.05). Conclusion Preoperative 2 ug/kg dexmedetomidine by nasal spray can effectively reduce the occurrence of negative postoperative behavioural changes.【Key words】 Dexmedetomidine by nasal spray;Negative Postoperative Behavioural Changes;Preschool children