This study examined the three issues that have been controversial in the studies on the Mongol-Oirad Code: Where was the meeting of Mongol-Oirad held in 1640? ; What was the role of the participants, who are written on the preface of the Mongol-Oirad Code? ; Who led the meeting practically? 1. Examining the two different views on the place of the meeting-Qalq-a or Oyirad, it was identified that the meeting had been held in Qalq-a, as Vladimirtsov advocated in 1930s and some scholars in later generations agreed. Yet, while the meeting place was likely to be Jasaγtu qan ayimaγ in Qalq-a, it was unable to confirm by materials. 2. A new interpretation was attempted on the role of the three lamas appeared on the preface of the Mongol-Oirad Code, especially the first appeared Inzan rinbüče with regard to his political activities. The author noticed that Inzan rinbüče had been involved in all major political events with respect to Qalq-a, Oyirad, and Mongolia-Tibet relationship such as the Qinghai campaign of Güši qaγan in 1636, the meeting of Širege-tü naγur in 1639, and the meeting of Mongol-Oirad in 1640. In the consideration of this, he might be not only the guarantor of the meeting and the Code of Mongol-Oirad but also the decisive figure who had arranged and accomplished the meeting. Then, reviewing the role of the twenty-eight nobles, unlike the traditional view that Bātur xung tayiji had drafted and others had just ratified it nominally, it was identified that they had participated in the actual enactment of these laws, referred to other cases and prefaces of the Mongol codes in those days. 3. Based on the critical review on the two different views regarding the leader of the 1640 meeting-Bātur xung tayiji of Jegünγar or Jasaγtu qan of Qalq-a, the author suggested a new interpretation in association with the major political events of Qalq-a, Oyirad, and Tibet in those days. Considering the Qinghai campaign of the meeting of Širege-tü naγur in 1639, and the meeting of Mongol-Oirad in 1640 as a series of political process that had interacted, it was assumed that the practical leader of all these events was likely to be dGe-lugs-pa, the religious body of Tibetan Buddhism. Considering such political situation in Mongolia at that time, the author recognized that it had to be the third power who had been able to assemble all the leaders in Qalq-a and Oyirad, and persuade to reconcile between each faction. Thus, there is a possibility that Inzan rinbüče was sent to Mongolia as the representative of the third power.