There are some relics of Princess Myeongan which are designated as National Treasure No 1220 in the City Museum located in Ojukheon, Gangreung city. These relics are quite valuable materials which are helpful to study Korean language(Hangeul), calligraphy, economy, social structure and courtly lifestyle of those times. These relics include six letters written in Korean by King Hyeonjong, Princess Myeongan`s Naming Paper written by King Hyunjong himself and two lists of Novels, the King sent to the princess. And three letters of Empress Myeongseong, King Sukjong`s Korean letters and several letters cherished by 0 Taeju(the son in law of King Hyeonjong) family are also contained in the list. In this paper, the letters of King Hyeonjong, Empress Myeongseong and King Sukjong contained in Empress Myeongseong`s Royal letter collection are examined. It has been known that of the royal letter written by in Korean language were mainly sent to the princess who had been married. But this royal letter collection of Empress Myeongseong contains letters sent to the mother of the King. Thus this letter collection shows the characteristics of courtly language.