simplification(CCS) in Korean can be explained in a unified mode applying OT. order not to violate the *Complex. It is the focus of this study to explore the consonants which are preserved. Generally, language universally and in other phonological processes in Korean, the syllable codas prefer the consonant of the higher sonorant if that syllable can not be an open syllable. Contrariwise, the Korean undergoes simplification by displaying a different pattem : simplified codas prefer the less sonorant consonant of the peripheral place. Thus, Nocoda-sonorant is low-ranked. This study claims that morphologically-based constraint(Parse-peripherality) is the main factor in determining CCS so that selected peripherals preserve the morpheme of the stem and eliminate the possibility of the non-peripheral coda being assimilated by the following onset. If morphological constraints can not decide a candidate, then phonological constraints evaluate the optimal output.