Korean peninsula was secession from WWⅡ and seventy years,however ancient Koren was unification about one thousand year.Only three kingdoms of Korean was secession.Silla,early so poor power kingdom,was unification. Whatever Korean peninsula usually was unification. Twice secession,three kingdoms of Korean was unification but now Chosŏn-Hanguk still was secession.The study want to discuss it by 3i decision model and level analysis.