Who is Dae Jo-young『 Where is he from』 These are the primary problems that we can face when we study on the history of Balhae. And < Shin Tang seo > and < Gu Tang seo > answer these questions with different statements : “Dae Jo-young of Balhae Malgal is original Byuljong of Koryeo.” in < Gu Tang Seo > but “Balhae originated from Songmalmalgal and then affiliated to Koryeo.” in < Shin Tang Seo >. These records are written in the beginning of the history of Balhae in these two literatures and they cause a lot of controversies about Dae Jo-yeongs native country. The key points of the controversies are these two literatures’ disagreement about Dae Jo-young and the matter of credibility- which literature is credible, < Shin Tang seo > or < Gu Tang seo >? Referring to previous historians’ researches on it I will analyze the usages of the term Byuljong used in ancient history literatures. Furthermore, I would like to study the opinion that Koguryeo is related directly to the phrase　“Balhae is ‘Byuljong’ of Koguryeo”. About the Balhae’s territory at that time when it had been founded, the nearby countries have had different views because they interpreted ‘Byuljong’ written in < Shin Tang seo > and < Gu Tang seo > according to their own interest. Through the previous researches we can find remarkable disagreement about the interpretation of Byuljong among them. The historians in South and North Korea describe ‘Byuljong’ as Koguryeo’s descendants or directly Koguryeo people. In Korea, some even insist that the founding father, Dae Jo-young, was a Songmalmalgal person who had been affiliated to Koguryeo and assimilated into it and he was also a general of Koguryeo. But the most of North East history scholars in China insist that the founding father of Balhae, Mr.Dae, was different from Koguryeo person, that is, he was Malgal person that’s why the term ‘Byuljong’ was used to explain him. This controversy about Mr. Dae is inevitable because not only ancient history literatures (< Shin Tang seo > and < Gu Tang seo >) wrote ambiguous statements about him but Balhae had consisted of various people from north east Asia. To reach a satisfactory settlement of considerable disagreement between historians of Korea and China about Balhae and Dae Jo-young, above all we may scrutinize the usage of the term ‘Byuljong’ in history. And we are likely to remember that it suggests complicated relationship among ancient nations and it also has various types of definition: the term of ‘Byuljong’ to clarify the origin of a nation, to classify political group, to be related with culture etc. We have often seen Byuljong in ancient history literature but its implication has not been clarified yet. Byuljong appeared in 『ThreeCountry History·Weihistory』 for the first time but it seems that many historians have used it as it is to describe ancient nations and their origin without interpreting the real meaning of it. ‘Byuljong’ may be understood as ‘different nation’ or ‘distinguished nation’ but you would know that it was mostly used to describe the relationship of ancient nations to examine the usage of ‘Byuljong’ in various history literatures. ‘Byuljong’ seems to be a customary and unclear term which ancient historians used to describe a nation origin and it was deeply connected with its mother nation in the middle of complicated relationship of ancient nations. These connection between ‘Byuljong’ and its mother nation had a lot of connotations : the order of each other’s beginning in chronicle, regional neighborhood or the same area of activity, cultural closeness, political affiliation and so forth. Furthermore, suppose one nation had belonged to its mother nation and then it became independent. In that case, we can easily confuse a nation with its mother nation and can’t clearly distinguish each other. This may be the reason ‘Byuljong’ was used. In fact, in ancient literatures ‘different nation’ was used when each other’s difference could be clarified; ‘Pescendants’ was used to express a nation`s descendants ; ‘rest of the nation to a nation’s survivors. Therefore the phrase “Balhae is original Koguryeo ‘Byuljong’” seems to be understood according to the point mentioned above, that is, Dae Jo-young, the founding father of Balhae would rather be understood as ‘Songmalmalgal person’ who had affiliated to Koguryeo and then assimilated into it than be described directly as Koguryeo person it means that 『Shin Tang seo』 and 『Gu Tang seo』’s differnt statements about Dae Jo-young and Balhae are complemented each other.