Due to various assimilation processes in the sound patterns of Korean, the language is called 'sea of phonology'. Among them, the place assimilation is reviewed. It is pointed out that previous works on Korean assimilation were not successful in explaining the process. Some attempts based on the theory of Optimaility also were discussed. A new analysis based on CT and PFT is proposed. Korean place assimilation is a result of the interaction among universal constraints such as Ons-Ident (place), Agree (place), Max (place) and Ident (place).