The subject of this paper is the theory of truth in the Saṃdhinirmocana-sūtra. The concept is based on two aspects of discussions: First is regarding the theory of truth as core content and main thread through Saṃdhinirmocana-sūtra, to reconsider its basic ideas and structure. This concept is different from previous researches which mainly focus on solving issues in sūtra from perspectives of “three characteristics” (trīṇi lakṣaṇāni), “three types of lack of own-being” (tri niḥsvabhāvatā), and “cognition-only” (vijñaptimātra) in Mind-only School. Second is since Saṃdhinirmocana-sūtra has the features of both sūtra and Māṛkās, while its main concept is influenced by Prajñāpāramitā-sūtra, especially the theories of emptiness and ultimate truth, and also developed continuously by Yogācāra School or Mind-only School as a scriptural source, this sūtra therefore has a characteristic of transition. Thus by discussing “the truth”, the common theme of Buddhism, within Saṃdhinirmocana-sūtra, dispute between Mind-only School and Mādhyamika School could be re-examined. In addition to introduction and conclusion, this paper consists of five chapters: The first chapter is the initial discussion of the theory of truth, which introduces the background of this paper. There are three parts in the first chapter: first of all, it is a brief overview of Western philosophy''s discussion of truth, “what is truth”, “how could we know the truth”, “how many theories of truth are there”, “what is the problem of them”, and so on. Second, the theory of truth in the Buddhism is expounded from both the theory of “four noble truths” (catvāri ārya-satya) and the theory of “two truths” (dvi satya), by using the text of Āgama, Abhidharma Mahāvibhāṣā Śāstra, and Mūlamadhyamakakārikā. Third, the theory of truth in the Yogācāra School is expounded from both the theory in the Yogācāra-bhūmi-śāstra and the theory of Madhyânta-vibhāga. The second chapter is the discussion of concepts about the truth in Saṃdhinirmocana-sūtra. Four concepts are discussed, including “ultimate truth” (paramārtha-satya), “emptiness” (śūnyatā), “suchness” (tathatā), and “the thoroughly established” (pariniṣpanna). Each of the four concepts is demonstrated in three aspects: “the meaning of the concept”, “understanding of the concept when used in context of Mind-only School”, and “understanding of the concept when used in Saṃdhinirmocana-sūtra”. At last, the relationship of these concepts is discussed. The third chapter is the discussion of the characters of ultimate truth. In this chapter, an interpretation is illustrated to help understanding the meaning of the second chapter of Saṃdhinirmocana-sūtra. There are four parts in
