Objective To study the 50％effective dose(ED50)and ED95 of remimazolam in the induc-tion of general anesthesia in preschool children,and to observe its safety and efficacy.Methods Children un-dergoing elective surgery who received endotracheal intubation and general anesthesia from March to October 2024 were selected as the research objects.The ED50 and ED95 of remimazolam were calculated by the modified sequential method.On this basis the additional,the aditional 68 subjects were randomly divided into the remimazolam group(group R,n=34)and the propofol group(group P,n=34).The respiratory rate(RR)and bispectral index(BIS)before induction(T0),1 min(T1)and 3 min(T2)after administration of remima-zolam or propofol in each group were recorded,and the oxygen saturation(SpO2),heart rate(HR)and mean arterial pressure(MAP)at T0,T1,T2,and 1 min after tracheal intubation(T3)were recorded.The success rate of sedation induction,hemodynamic stability and the incidence of adverse reactions such as injection pain,bradycardia,hypotension and panic during induction were compared between the two groups.Results Probit regression analysis showed that the ED50 of remimazolam for inducing loss of consciousness in preschool chil-dren was 0.414 mg/kg,95％CI:0.381-0.448,and the ED95 was 0.474 mg/kg,95％CI:0.443-0.826.The success rate of sedation induction in both groups was 100％.The disappearance time of eyelash reflex in group R was(59.44±5.24)s,which was longer than(29.79±4.04)s in group P(P＜0.001).The RR and BIS of group R at T1 and T2 were higher than those of group P,and the HR and MAP of group R at T1,T2 and T3 were also higher than those of group P(P＜0.05).The incidence of injection pain,bradycardia and hypoten-sion in group R was lower than that in group P(P＜0.05).There was 1 case of panic in group R.Conclusion The ED50 and ED95 of remimazolam for loss of consciousness during general induction in preschool children are 0.414 mg/kg and 0.474 mg/kg respectively.It has a definite sedative effect,stable hemodynamics and a low incidence of adverse reactions for the induction of general anesthesia in this population,demonstrating its suit-ability for clinical use.