Background:The development of auditory and speech perception ability of children with hearing toss is affected by many factors after they undergo cochlear implantation (CI).Age at CI (CI age) appears to play an important role among these factors.This study aimed to evaluate the development of auditory and speech perception ability and explore the impact of CI age on children with prelingual deafness present before 3 years of age.Methods:Two hundred and seventy-eight children with pre-lingual deafness (176 boys and 102 girls) were included in this study,and the CI age ranged from 6 to 36 months (mean age,19 months).Categorical auditory performance (CAP) was assessed to evaluate auditory ability,and the speech intelligibility rating was used to evaluate speech intelligibility.The evaluations were performed before CI and 1,3,6,12,18,24,36,48,and 60 months after CI.Results:The auditory ability of the pre-lingually hearing-impaired children showed the fastest development within 6 months after CI (k =0.524,t =30.992,P ＜ 0.05);then,the progress started to decelerate (k =0.14,t =3.704,P ＜ 0.05) and entered a plateau at the 24th month (k =0.03,t =1.908,P ＜ 0.05).Speech intelligibility showed the fastest improvement between the 12th and 24th months after CI (k =0.138,t =5.365,P ＜ 0.05);then,the progress started to decelerate (k =0.026,t =1.465,P ＜ 0.05) and entered a plateau at the 48th month (k =0.012,t =1.542,P ＜ 0.05).The CI age had no statistical significant effect on the auditory and speech abilities starting at 2 years after CI (P ＞ 0.05).The optimal cutoff age for CI was 15 months.Contusions:Within 5 years after CI,the auditory and speech ability of young hearing-impaired children continuously improved,although speech development lagged behind that of hearing.An earlier CI age is recommended;the optimal cutoff age for CI is at 15 months.