This study analyzes the Baekche official costume system, including the dress, cap and belt systems, by relating documentary records with the results of excavations. The study shows that the system differed depending on the time. A system of dress based on official ranks was instituted during the region of King Goi in the third century. The rap amd belt systems were begun in the first half of sixth century The official costume system, as recorded in the Chinese history $Sus{u{o}}$, included many subdivisions of cap colors, which followed belt colors. According to $Gudangs{u{o}}$, dress and cap systems changed in the seventh century. The official costume consisted of a $jacket(j{u{o}}gori)$, trousers(baji), and coat(po). The coat had wide sleeves and reached below knees. Its collar had straight neckline. Officials of all rank wore silk caps and belts of matching colors. Officials above sixth rank used silver flower decorations on their caps. Officials wore wide-crouch trousers and generally adjusted the hems of the trousers, but this practice stopped in the sixth century. Officials wore shoes or boots depending on occasion. From a historical viewpoint, Baekche is important for having been the first Korean kingdom to establish a government organization. The salient feature of the system of organization established in A.D. 260(the twenty-seventh year of the region of King Goi) was the application of different colors to identify different ranks.