When it comes to the invention of Hunminjeongeum, it has been overlooked that the new letter system was purposely made to establish the throne of Joseon Dynasty. Here this untreated issues are dealt by reviewing several articles in the Annals of the Joseon Dynasty. In Section 2, the reasons why the Hunminjeongeum was invented are studied with the article of Feb 20 of 26 Annals. This article contains significant information about the process of inventing Hunminjeongeum and literary policies in the era of King Sejong as well. Thus reviewing the article led to revealing the dynamics between the king and his officials in the Royal Court which had neglected in previous studies. For example, appeals submitted by Choei Manri turned out to be the attempt to control the throne with the "Sadae" diplomatic policy and Confucianism. King Sejong however beat off the challenge by laying out logical bases, and it affected other counter arguments against the letter invention. Ever since these appeals had been dealt with, the literary policy went well. In Section 3, the historical background that needed new character system, Hunminjeongeum is mainly reviewed. In the early years of the Joseon Dynasty, the literary policy was established in relation to organizing national administrative systems domestically. It was also related with making its place in the East Asia internationally. The throne needed its authority recognized both internally and externally, so made its own character system and new Unseo(Dictionary of Proper Pronunciations) to achieve the goal effectively.