The purpose of this studied was to examine the reliability analysis of the GMFM in children with C.P. The subject of this study were 40 C. P patient who had been hospitalized Department of Sam-Yook Rehabilitation Hospital. Subjects were 28 boys and girls, aged 6 to 8 years. Reliability of each dimension of the GMFM were analyzed using Cronbach coefficients and to examine the intra-rater reliability were using Pearson correlation coefficients. The result of reliability analysis of the GMFM revealed higher reliability values. The reliability of the total dimension score was 95. Test-retest revealed intra-rater correlation coefficients from .71 to .98. The study presents that GMFM is useful in assessment of function of children with C. P by the quantitative description of the function.