This paper proposes that phonology for adopted English words is independent of native Korean phonology in the aspects of syllable structures. I show that unmarked syllable structures emerge when English loanwords are adopted into Korean and argue that within the framework of Optimality Theory, loanword phonology and native phonology can have different constraint hierarchies. Further, I show that loanwords do not have a single pattern and must be categorized into several types, which bear different constraint rankings. Loanword phonology should have a multiple constraint ranking rather than a single constraint ranking.