The goal of this study is to verify the effect of phoneme-centered writing on the writing ability of children with intellectual disabilities who have a difficulty in telling and can understand the order of teacher. In order to verify the effect on the writing ability of children with intellectual disabilities, pre-test/post-test design was used. This study verified the effect of the writing precision and the writing speed subjecting on three male students who are currently attending as 2nd grade in Y special elementary school, Y city. Selection criteria of study subjects are (a) child with 55 or less intelligence quotient, (b) child with 69 or less adaptive behavior quotient, (c) child with 11 or less chronological age, (d) child who can use pens, and (e) child who can understand the order of teacher. Phoneme-centered writing program was conducted in order of writing vowels and consonants by adding, writing one syllabic word by adding, writing 2~4 syllabic words by adding, and writing one phrase or sentence by adding. After writing words by dividing into consonants and vowels, write the word by combining consonants and vowels. This study was conducted in writing precision and writing speed aspects using writing evaluation form implemented respective three times per pre- and post-test. As a result, phoneme-centered writing program showed the improvement in the writing ability of three subjects. In writing precision aspect, subjects showed the improvement in average scores of post-test comparing to pre-test for the degree of 5.3, 5.4, and 7 respectively. In writing time, they showed the improvement in writing speed by shortening writing time in post-test comparing to pre-test.