The purpose of this study was to compare prosody characteristics between mentally retarded children and normal children and suggest preliminary materials to improve mentally retarded children\'s communication ability by using proper prosody. The subjects who participated in this study were 20 mentally retarded children and 20 normal children in 4 groups as 18-month-old(one-word stage), 24-month-old(two-word stage), 36-month-old(three-word stage) and 48-month-old(sentence stage), and examined the utterance of 10 communication functions(questioning, calling, answering, greeting, requesting, asking, protesting, emotion expressing, insisting and suggesting) by CSL(Computerized Speech Laboratory) to compare their pitches, intensities, duration ranges, pitch contour patterns, and characteristics of final syllable intonation. The results were as follows; First, There was no difference between 18-month-old(one-word stage) mentally retarded and normal children in their pitches, intensities and duration ranges, while they showed the dissimilarity of pitch contour pattern in 6 functions, greeting, requesting, asking, protesting and suggesting. For the final syllable intonation, both groups mostly used L(flat contour) and both groups used R(rising contour). Second, in 24-month-old group(two-word state), mentally retarded children used lower pitches and intensities than normal children in all of 10 communication functions, and two groups showed the pitch contour pattern differences in every function except suggesting. In the normal group, high frequency consonant (ㅊ, ㅎ, ㅈ,ㅍ, ㅅ, ㄱ) was produced with high pitch while mentally retarded group produced with low pitch and intensity. For the final syllable intonation, both groups mostly used F(falling contour) and the normal groups used RF(rising and falling contour) more. Third, in 36-month-old group(three-word state), the mentally retarded used higher pitches than the normal in 9 functions which excludes greeting, and took longer duration to operate 9 functions which excludes insisting. In 36-month-old groups, the mentally retarded group used higher pitches except the greeting and took more time except insisting. The mentally retarded group showed higher pitches(usually found in 24-month-old normal children) in appearance of /ㅅ, ㅈ, ㄱ/ to indicate they were retarded in phoneme utterance of high frequency. The retarded group seemed similar to the 24-month-old(F>L>R>RF) in the intonation of the final syllable; yet, they expressed their purposes of communications more naturally by final syllable intonation. Fourth, in 48-month-old group(sentence state), the mentally retarded group used higher pitches than normal children in six functions(questioning, calling, answering, greeting, protesting, and insisting) and kept high pitches(1000Hz) as same as the mentally retarded 36-month-old group while normal children decreased their phoneme utterances in high frequency(800-900Hz). Moreover, both groups used flat or falling contour in a choice-interrogative complex sentence and showed unique pitch variations in sentence level stressed phrases with four syllables and less that were different from adults\'.