This study was analyzed to change of /i/ formant follow cochlear implantation periods for hearing impaired children with cochlear implantation. 20 hearing impaired children participated and acoustic analysis of /i/ was used CSL(Computerized Speech Lab; Model 4300b) annually. The data was captured the first formant, $2^{nd}$ & 3th formant frequency of /i/ and was analyzed using ANOVA. Multiple range test to investigate difference between group was treat with LSD and Duncan. The results of /i/ formant analysis for hearing impaired children with cochlear implantation, each formant at a year keeping with cochlear implantation was located at high frequency. In accordance with CI periods, the each formant decreased significantly, especially between a year and $2^{nd}$ year taking with cochlear implantation.