This article investigates the philosophy of the Lotus Sūtra as interpreted by Hanshan Deqing in late Ming China. It will focus on his doctrinal classification (panjiao 判教), present his structural analysis of the text (kepan 科判), and examine the theory of true mind (zhenxin 真心) and true reality (shixiang 實相). Borrowing the five-part scheme of doctrinal classification from the Huayan School, he viewed the Avatamsaka Sūtra as the “perfect teaching” (yuanjiao 圓教) and the Lotus Sutra as the “Advanced Mahāyāna teaching (zhongjiao 終教).” For Deqing, the core meaning of these two sutras is the same, so he used the former sutra to interpret the latter one. Deqing suggested that the teachings in the Avatamsaka Sūtra and the Lotus Sūtra are the same when seen from the highest level of Buddhist reality. However, the meaning of his “Advanced Mahāyāna teaching” is different from that of the Huayan School. Deqing’s “Advanced Mahāyāna teaching” represents the end of the Buddha’s teachings as explained from the perspective of the Buddha’s teaching method. This view is different from the “Advanced Mahāyāna teaching” of the Huayan School which emphasizes the doctrine of all sentient beings’ potential attainment of Buddhahood. As for Deqing's structural analysis of the text of the Lotus Sūtra, inspired by a paragraph in the text, Deqing divided the main body of the text into four parts: teaching (kai 開) the Seeing and Knowing of the Buddha (fozhijian 佛知見), displaying (shi 示) the Seeing and Knowing of the Buddha, understanding (wu 悟) the Seeing and Knowing of the Buddha, and penetrating (ru 入) the Seeing and Knowing of the Buddha. At the first stage, the Buddha taught that the mind of an audience is the mind of the Buddha, and the Buddha led his audience to believe this fact. Then, he displayed the true object of the Dharma-body, and he led the audience to know that the true mind and the true object are one. At the third stage, he showed the entirety of his own Dharma-body to enhance the audience's level of understanding. The last part presents the highest level of Bodhisattva practices to help the audience sweep away the deepest defilements. Deqing’s structural analysis of the text expanded the meaning found in Buddhist scriptures. Deqing considered “penetrating the Seeing and Knowing of the Buddha” the most important concept in the Lotus Sūtra. Thus, the proper understanding of this concept is crucial to comprehending the deep meaning of this text. For a clear interpretation of the Seeing and Knowing of the Buddha, Deqing skillfully divided the Buddha’s wisdom into two parts: 1) the mind, as subject, sees the true reality of the Dharma realm, and it produces the Buddha’s true and expedient teachings. 2) The object perceived by the mind displays the entirety of the Dharma body, and this fact can be explained through the theory of the perfect and endless Huayan Dharma-realm. Deqing follows the doctrines of the Lotus Sūtra to show the profound meaning of the Seeing and Knowing of the Buddha.