It is of great significance to perform a ceremony with the utmost honor in every society and the fact is that ancient Koreans executed sacrificial rites to natural scenery with primitive reilgious things from the beginning of Korean history. Minute records on the various ceremonies to the Koryeo Dynasty are found in Koryeodogyeong and it might be said that there were no standing rules and the many ceremonies were resorted to an expedient, because in the Yi Dynasty the first codified ceremonial lawbook, Kukjooryeeui was formalized and after then all the ceremonies and formalities were carried out by the referential rules of the above-mentioned Kukjooryeeui. After the imperial enthronement of Kojong, all the ceremonial goods and flags symbolizing the heaven and auspicious animals-authority and fortune-were made by Daemyeongjibyei, which are found at Changdeokgung now. There are no remarkable differences in the Yi Dynasty between the records at the beginning and the remaines at the last stage, which shows once-fixed standing rules were kept faithfully to the end. The main patterns used on flags were of imaginary animals such as dragon, indicating the wish that countless authority and fortune should be realized. This is the former part of the study on the ceremonial flags in the Yi Dynasty and I hope the detailed idea and symbolic meaning concerning the flags will be discussed later.