This study is to compare the structure and derivation form of onomatopoeia (mimetic) words in Korean and Chinese languages. Because two different languages not only in language form, but also in structure would definitely havecertain influence on word forms and derivation of onomatopoeia and mimetic words. Although it’s an elementary way, however, this study leads to the conclusion as below regarding word form and derivation of onomatopoeia (and mimetic) words in Korean and Chinese languages(The study in Chinese language is limited to onomatopoeia. Because the most of mimetic words in Chinese standard languageis derived from general adjective or verb, in other words, the pure mimetic words such as ‘DegulDegul(데굴데굴)’ in Korean don’t exist in Chinese language.) (1) It’s easy to find onomatopoeias (and mimetic) words which consist of four or six syllables in Korean language, while there are usually four-syllable onomatopoeias words in Chinese language. (2) A mono-syllable word(A type) or two-syllable word(AA type, AB type) can be the root (fundamental form) in Korean language. The derivation process from the root shows wide range of AB type usage, which tells us the Korean onomatopoeias and mimetic words which consist of three, four, or six syllables are generally derived from the root AB type. On the other hand, Chinese onomatopoeias are mostly (or altogether) derived from the root with the monosyllable, A type (fundamental form).AA type indicates the duplicated usage of A type monosyllable which can be used as an independent word by itself, whileAB type indicates the modified usage of A type monosyllable, or combined usage of separately independent two mono-syllables. Onomatopoeias with three syllables or four syllables are eventually the modified form of AB type with A type monosyllable root. (3)The modified duplicate usage among Korean onomatopoeias and mimetic words usually changes the initial and middle sound in two-syllable words(AB-AB or ABC-ABC), but Chinese onomatopoeias changes the vowel sound of previous syllable or the initial consonant sound of next syllables. (4) In Korean onomatopoeias and mimetic words, the substitution of initial consonant sound and the interchange of middle vowel sound cause the subtle transition of nuance. However, there is no such interchange in Chinese onomatopoeias. (5) AB type onomatopoeias and mimetic words in Korean language lead to various types of ABC onomatopoeias and mimetic words by partial duplicate usage or added sound. Contrastively, there are no same cases in Chinese language, where ABC type syllables are derived from AB type syllables.