The purpose of this paper is to investigate phonological characteristics in Cheonmyeong Noh and Yunsuk Mo`s poems on the basis of syllable structure. As a methodology, I have divided the syllables of poem into onset, nuclear, and coda, then investigated the phonemic frequencies of each element. Cheonmyeong Noh and Yunsuk Mo`s works have been illuminated sufficiently in view of literary theories. However, they have scarcely been studied in terms of their linguistic aspects. Poetry is based upon the relationship of similarity among sounds. Sounds perceived as similar to one another create acceptable rhythm pairs. Because sounds are hierarchically arranged in languages, patterns in poetry can reveal the priority order within this hierarchy. So, with respect to the phonological patterns of Korean, I have analyzed all of Cheonmyeong Noh and Yunsuk Mo`s works. At last I find the priority order of Cheonmyeong Noh and Yunsuk Mo`s poems within sound hierarchy. Most common are syllables with no onset and no coda pairs. With respect to acoustic features, the most frequent syllable utilize the sonorant feature. This pattern remains consistent over time.