Balhae kingdom(渤海國) was a country that was formed by multi ethnic groups and among those multi ethnic groups, the people of Koguryo(高句麗) origin and Malgal(靺鞨) origin constituted the majority of the Balhae people. The remaining issue is which of those two ethnisities the leading and central ethnic group in Balhae was. Concerning the origin of the royal family, the house of Dae (大氏). Xitangshu(新唐書) and Jiutangshu (舊唐書) transmit different stories respectively, and these two different stories have been parallelled so far in the understanding of this issue. In this process, several hypothesis have been suggested, in which the articles concerned in two historical documents are synthesised. One of the examples is that Daejoyoung (大祚榮) was described as Gaolibiezhong(or Kyryo Byeoljong, 高麗別種) in Jiutangshu (舊唐書), and biezhong(Byeoljong, 別種) here means a group that was ethnically different from the Koguryo people but politically subordinate to it. It has been also argued that if so, Gaoli Biezhong (or Koryo Byeoljong, 高麗別種) in Jiutangshu corresponds to the historical record in Xin Tangshu, in which the Daejoyoung group originally belongs to Sokmal malgal (粟末靺鞨) and is politically subordinate to Koguryo(高句麗). However, this hypothesis does not coincide with the substantial examples of Biezhong (or Byeoljong) used in this period. Biezhong( Byeoljong,別種) means Zhi pai(or Jipa, 支派) or Bie pai (or Byeolpa, 別派), a group of a branch. The second hypothesis is to synthesise the two different stories concerning the origin of the Daejoyoung(大祚榮) group in an eclectic way. This is called the hypothesis of Yemaecmalgal (濊貊靺鞨). Malgal(靺鞨), which has been found in historical documents, and can be actually divided into two Malgal (靺鞨) groups, that is to say, Yilouxi(or Uplugye malgal, ?婁系 靺鞨) and Yemaecgye malgal (濊貊系 靺鞨). Sokmalmalgal (粟末靺鞨) and Baeksanmalgal (白山靺鞨) belonged to Yemaecmalgal (濊貊靺鞨) and they became Balhaemalgal (渤海靺鞨). This hypothesis argues that Yemaecjok(濊貊族) and Malgaljok(靺鞨族) are originally the same, because Malgal (靺鞨) resided in the place of Yemaec (濊貊), such as Buyeo, Dongye and Okjeo. This argument, however, ignores the historical fact of the migration of peoples and attempts to connect directly the two historical records that have temporal gaps with each other and to understand them statically. Therefore, the substantial admissibility of evidence of this hypothesis cannot be accepted. The third hypothesis about the constitution of people in Balhae and its central leading ethnic group is the fusion of ethnic groups, that is, the supposition of 'Balhae-ite'(渤海人) as the central group to lead Balhae. In fact, after the fall of Balhae, the people were clearly divided into Balhae-ite(渤海人) and Jurchen-ite(女眞人). Balhae-ite was the existence differentiated from Jurchen-ite in social and cultural aspects and even in terms of consciousness. In this respect, Balhae-ite existed as an ethnic group. Then the question raised is when this Balhae-ite was formed and how its ethnic genealogy and character can be grasped. For this question, there is a perspective to see this Balhae-ite as succeeding Sokmalmalgal(粟末靺鞨) or Koguryo-ite (高句麗人). In this case, this argument asserts that Bahae was a state of Sokmalmalgal(粟末靺鞨) or Koguryo-ite and its character is laid on the extension of that prior to the establishment of Balhae. This is a non-historical understanding that fails to grasp the character of Balhae dynamically and furthermore, it lacks any substantial evidence to support it. It has been proven by written documents that a part of the Malgal tribe as well as the Koguryo people participated in the establishment of Balhae and this fact is also supported by archaeological research. The only problem is which ethnic group of Koguryo played a central role in the fusion of the two ethnic groups and what extents its fusion progressed in social and regional aspects. This question can be resolved by detailed examinations of the material cultures of each region drawn from archaeological excavations in the future. For this, it is of necessity to grasp the detailed situation by archaeological excavations carried out within the old territory of Balhae and to accumulate data incessantly. In fact, the question of which ethnic group led Balhae is not only one of substantial evidence, but also of historical consciousness. This is proved by the fact that each country claims completely different arguments about this sensitive question following its own research history. Instead of being absorbed by one-sided nationalism, having a well-balanced historical consciousness is the key factor to progress in further research.