Abstract: Objective: To explore the clinical effects of different doses of remifentanil on the spontaneous respiration in children under the sevoflurane anesthesia.Methods: Eighty children treated with inguinal hernia repair operation were randomly divided into the low dose group and high dose group according to the use dose of remifentanil(40 cases each group).The anesthesia in low dose group and high dose group were maintained using 0.03μg·kg^-1·min^-1 and 0.09μg·kg^-1·min^-1 of remifentanil,respectively.The respiration rate(RR),tidal volume(TV),minute ventilation(MV),partial pressure of carbon dioxide in endexpiratory gas(PCO₂),mean arterial pressure(MBP) and heart rate(HR) were recorded at T₀(intubating laryngeal mask airway),T₁(after intravenous loading),T₂(after 10 min of anesthesia),T₃(after 15 min of anesthesia) and T₄(extracting laryngeal mask).The occurrence of intraoperative anoxenia in two groups were analyzed.Results: The levels of RR and MV in two groups significantly decreased at T₁(P<0.01),and the levels of RR and MV in low dose group at T₂,T₃ and T₄ were significantly higher than those in high dose group(P<0.01).The levels of PCO₂ in two groups significantly increased at T₁,and the levels of PCO₂ in low dose group at T₂ and T₃ were significantly lower than those in high dose group(P<0.01).The differences of the level change of VT,HR and MBP in two groups at each time point were statistically significant(P>0.05).The intraoperative anoxenia was not found in two groups.Conclusions: The effect of sevoflurane combined with low dose remifentanil in spontaneous respiration anesthesia in children is good,which can make the respiratory system more stable in children,and has application value in clinic.