This paper explores how the Three Ministries-Six Departments system was created in the early Goryeo period and how it was transformed later. The Three Ministries-Six Departments originated above all from Gwangpyeong Ministry (廣評省), Naebong Ministry (內奉省) and Naeui Ministry (內議省) among various authorities. Gwangpyeong Ministry and Naeui Ministry were dissolved and their functions were absorbed in Munha Ministry (門下省) and Naesa Ministry (內事省). Some functions of Naebong Ministry were transferred to Eosado Ministry (御事都省). Naebong Ministry's of right of personal management, Byeongbu and Changbu were transformed to become Eosaryukgwan (御事六官), which is similar to the Ryukjeon System (六典組織) of the Tang Dynasty.
The three ministries in the first year of the King Seongjong (982) were Naesa Ministry, Munha Ministry, and Eosado Ministry. The Naesa Ministry and Munha Ministry, which were made in the first year of Seongjong on the model of the system of the Tang Dynasty, and Naesa Ministry was reformed to Jungseo Ministry in the 15th year of Munjong (1061), following the system of Song Dynasty; thus Jungseo Ministry and Munha Ministry were formed. The case of Sangseo Ministry, however, was somewhat different. Sangseo Ministry was reorganized to Eosado Ministry (御事都省) and Eosaryukgwan, which were created in the first year of the King Seongjong, and rearranged to Sangseodo Ministry (尙書都省) and Sangseo Six Departments(尙書六都) in the 14th year of Seongjong, following the system of the Tang Dynasty. At last, these are still to be rearranged to Sangseo Ministry and Sangseo Six Departments in the 15th year of the King Munjong (1061) after the model of the Song Dynasty.
The Three Ministries-Six Departments of the early Goryeo Dynasty was transformed to result in the "One Department(一府: Cheomui Department 僉議府, Dopyeonguisasa 都評議使司)-Four Offices (四司)", which existed in the period between the first year of the King Chungryeol when Jungseo Ministry and Munha Ministry were combined to become Cheomui Department (1275), and the 5th year of the King Gongmin (1356) when they were reduced again to the 'Three Ministries-Six Departments'. In the 11th year of the King Gongmin (1362), Sangseo Ministry was dissolved, and "One Department (一府, Munha Department 門下府)-Six Offices (六司)" came to be a main system in the period from when the Jungseo Ministry and the Munha Ministry were unified to become Docheomui Department (都僉議府) in the first year of the King Gongyang (1389) in the end of the Goryeo Dynasty. In short, in the later part of the Goryeo Dynasty, "One Department-Four Offices" changed to "One Department-Six Offices". In the first year of the King Gongyang, the Six-Jo (六曹) came to belong to Munha Department. Thus, "Three Ministries-Six Departments" of the Goryeo Dynasty underwent a great deal of transformations, being connected to the Uijeong Department (議政府) and Six-jo in the Joseon Dynasty.