The purpose of this paper is to reveal the identity of Gyeongsa 景師 as mentioned in the Yugaron-gi 瑜伽論記: his name, hometown, writings, the trends and characteristic of his thought. The Yugaron-gi, or Commentaries on the Yogâcārabhūmi-śāstra, was written by Doryun 道倫, a monk from Silla. Importantly, the Yugaron-gi contains many commentaries written by monks from Silla, but only some explicitly mention their Silla nationality on the annotations. In previous studies, most researchers have considered Gyeongsa 景師 as being Hyegyeong 惠景, a monk from Silla. In this paper, I also develop my discussion as an extension of this argument. In particular, considering the fact that Gyeongsa was mentioned together with Weoncheuk 圓測 and Sungyeong 順憬, who were definitely from Silla, I think this assumption is very persuasive. To understand Hyegyeong's writing and the trends of his thought, I first analyze Hyegyeong's commentary shown in the Stage Associated with the Five Bodily Consciousnesses 五識身相應地 and Stage of Mental Consciousness 意地. Examining the orders these commentaries were quoted, there were many cases, naturally, with the order of 'Hyegyeong 惠景 – Gyugi 窺基', and less commonly, the order of 'Samjang 三藏 – Hyegyeong'. Through the former case, it is clear that the most important figures that influenced Doryun's composition of the Yugaron-gi were none other than Hyegyeong and Gyugi. Gyugi in particular demonstrates that he established his points of view on a foundation of actively accepting Hyegyeong's opinions. This fact is also corroborated in previous research, clearly showing Hyegyeong's doctrinal authority in the Commentary on the Yogâcārabhūmiśāstra 瑜伽師地論. Looking into Hyegyeong's commentary, it proves that he was very conversant with scholarship of Mahayana and Theravada Abhidharma. For example, looking at his commentary on 'Connecting the wholesome roots of virtuous merit 續善根' and 'Matter 色法', he exactly points out the differences of defining these concepts between Mahayana and Theravada. Next, it is also very distinctive that Jinje's 眞諦 commentaries 疏 and translations appear frequently among the literature Hyegyeong quotes. This fact shows that he was not only conversant with new translations of Yogâcāra treatises, but also with the old ones translated by Jinje. Through these findings, it is likely that Gyeongsa was not just a figure who left commentaries on the Yogâcārabhūmi-śāstra – there is a high possibility that he was in fact 'Seomyeongsa Monk Hyegyeong 西明寺沙門慧景' who served as initial checker when Xuanzang was translating Da piposuo lun 大毘婆娑論. The Commentary note of Seopdaeseungron-Gyeongbeopsa Cheonchingoron 攝大乘論疏 ⼞卷– 景法師 天親古論 shown in Dongyeok jeondeung mokrok 東域傳燈目錄 may also be written by Gyeongsa. In conclusion, Gyeongsa, or Hyegyeong, worked in the same period of time to Weoncheuk. Although he mainly studied the old treatises of Yogâcāra, when the new translations of Yogâcāra were translated, it appears that he became a learned monk famous for his study of the Yogâcārabhūmi-śāstra. This part related to the Yogâcārabhūmi-śāstra can be verified through Gyeongsa's Yuga ron bogweol 瑜伽論補闕, frequently quoted in Yugaron-gi.