As the founder of the first Buddhist school - T'ien-t'ai Buddhism in China, master Chih-i's indispensable contribution toward the establishment of Chinese Buddhism is reflected mainly in his ingenious interpretation of one of the most important Buddhist scriptures - the Lotus Sutra (Saddharmapundrikasutra). This is because such an interpretation is not simply the interpretation of the scripture, but more significantly, through his systematic exposition of the Lotus Sutra, Chih-i expresses his own philosophical thought. Precisely speaking, the interpretation itself is a concrete demonstration of Chih-i's own philosophical system of understanding Buddhism. In this paper, I will deal with Chih-i's system of sign interpretation, which is discussed under eight categories. The source work of this study is based on Chih-i's gigantic work The Abstruse Meaning of the Sutra of the Lotus Flower of the Fine Dharma (Taisho vol. 33, no. 1716). This study reveals how Chih-i creatively interprets the Lotus Sutra, and how his perfect harmonization philosophy is at work through his system of sign interpretation.