The direction and conclusion of the study undertaken in this thesis are shown as follows. First, in order to find out the accurate time of the era name of Goguryeo as confirmed in a number of epigraph, the naming an era method of Goguryeo was reviewed first. As a result, it was confirmed that Goguryeo followed the method[踰年稱元法] that the naming an era was made in the year after the preceding king passed away. And, second, the periods of each era name of Goguryeo that was shown on the epigraph are finalized as follows: first year of Youn-su(延壽) = 451, 7th year of Youn-ga(延嘉) = 539, 7th year of Young-gang(永康) = 551, 4th year of Kyung▨(景▨) = 571, 5th year of Kun-heung(建興) = 596, and 3rd year of ▨hwa(▨和) = 606.
As a result of reviewing the operation and change era name method for the era name of Goguryeo on the basis of the deployment trend of the aforementioned era name, following facts could be observed. First, the Era Name Young-lak of the reign of King Gwanggaeto was used throughout the entire period of its ruling without the change era name during the kings reign. However, from the rime of King Jangsu, as confirmed through the Era Name Youn-su, the change era name was attempted during the term of the king. Second, in the later period of Goguryeo, the new kings had the change era name in the third year of the reign after completing the 3-year mourning period of the preceding king, or if it follows the method [踰年稱元法] that the naming an era was made in the year after the preceding king passed away, the change era name was undertaken in the second year in the throne. Third, as in the case of the Era Name Young-su under the reign of King Yangwon, if the preceding king died under the emergency situation, such as a political upheaval, the change era name took place immediately following the method to take the throne right after the death of the preceding king [卽位年稱元法]. And, fourth, as in the Era Name during Kyung▨ under the reign of King Pyeongwon or the Era Name ▨hwa during the reign of King Yeongyang, the change era name following the enormous building campaign in the nation or change in the international political situation was undertaken.