This paper is a preceding work for reflecting morphologic and syntactic properties of Korean inflectional affixes. I introduce the method and principle of HPSG for its discussion. First, I add a new morphological unit to the sub-classification of sign in P&S(1984) and establish the schema for the morphological unit. And I explain that the Korean inflectional affixes unite the Korean verb stem and other inflectional affixes as a agglutination and linguistic information of Korean inflectional affixes unite the linguistic information of Korean verb stem and other inflectional affixes as the principle of `unification`.