AIM: To investigate the effect of the timing of satisfactory sedation with preoperative oral midazolam on anesthesia induction and recovery in children undergoing adenotonsillectomy. METHODS: A total of 147 children undergoing elective adenotonsillectomy, with ASA physical status ⅠorⅡ, aged 2-7 years were selected from November 2022 to June 2023 in the Second Affiliated Hospital of Wenzhou Medical University. The children were orally administered 0.5 mg/kg midazolam in preoperative waiting area and were divided into 10-20 min (rapid onset, M1 group) and 21-30 min (slow onset, M2 group) based on the satisfactory sedation time, or equal volume of sugar pear drink orally (blank control group, C group). Children in all three groups received a general anesthesia method of propofol+fentanyl combined with sevoflurane induction and sevoflurane maintenance. The primary outcome measures were the induction compliance checklist (ICC) score and the pediatric anesthesia emergence delirium (PAED) score in the post-anesthesia care unit (PACU) to assess the occurrence of emergence agitation (EA), and the secondary outcome measures included the parental separation anxiety scale (PSAS), sedation Ramsay score, surgery duration, recovery time, PACU stay time, discharge time, the incidence of perioperative respiratory adverse events (PRAE) and other adverse events in the ward. RESULTS: 147 children were included in the result analysis, with 49 cases in each group. The proportion of perfect induction (ICC=0) were significantly higher in two M groups than that in group C (95.9% vs. 91.8% vs. 61.2%, P=0.001). The maximum and average PAED score in PACU in group M1 showed a significantly higher (6.4±5.0 vs. 4.4±4.1, P=0.029; 5.2±4.5 vs. 3.4±3.6, P=0.030), and the incidence of EA was significantly higher than those in  group C (10.2% vs. 30.6%, P=0.022), and increased compared to the group M2 (OR=0.581, 95%CI 0.231-1.463, P=0.354). There was no statistically significant difference in the maximum and average PAED scores, incidence of EA between group M2 and group C (P>0.05). The Ramsay score and PSAS score in two M groups were higher, PACU stay time and recovery time was longer than those in group C (P<0.05). The pain scores in PACU in group M1 was higher than that of group C (P<0.05). There was no statistically significant difference in the surgical time, discharge time, the incidence of PRAE and other adverse events in the ward among three groups (P>0.05). CONCLUSION: Preoperative oral midazolam can improve the ICC and PSAS scores of children during induction, but it also leads to prolonged recovery time and PACU retention time. The rapid onset of midazolam did not result in better induction and recovery quality, but instead increased the incidence of EA and postoperative pain score.