Objective: To investigate the clinical effect of different doses of esketamine in preventing emergence agitation (EA) in children under sevoflurane general anesthesia. Methods: 80 children who underwent elective tonsillectomy or (and) adenoidectomy in our hospital were selected. The children were allocated randomly to one of four groups receiving saline(group C), esketamine hydrochloride 0.25 mg/kg (group K0.25), esketamine hydrochloride 0.5 mg/kg (group K0.5)or esketamine hydrochloride 0.75 mg/kg (group K0.75) . The children in each group were administered the study drugs 10 minutes before the end of surgery.All children were maintained anesthesia with sevoflurane. The recovery characteristics, including the time to extubation, delivery time from the PACU, postoperative nausea and vomiting, agitation and modified CHEOPS score were recorded and analyzed. Results: Immediately after extubation, the modified CHEOPS score and postoperative recovery agitation score of the three groups of children receiving intravenous esketamine were lower than those of group C (P<0.05), but there was no statistical difference between the three groups significance (P>0.05). When leaving the PACU, the postoperative awakening agitation scores of the children in the K0.25 and K0.5 groups were lower than those in the C group (P<0.05), but there was no significant difference between the K0.75 and C groups (P> 0.05). Compared with group C, postoperative extubation time and PACU stay time were significantly prolonged in K0.75 and K0.5 groups (P<0.05). Conclusions: Low-dose (0.25 mg/kg) of esketamine hydrochloride can reduce the incidence of emergent agitation and postoperative pain,and has little effect on anesthesia recovery.