Siddham literature plays a very important role in Buddhist practice since the principles regarding how to pronounce mantras are embedded. That is what people used to say: “A word contains a dharma-door which is a key to enlightenment.” The knowledge of Siddham is indeed a kind of valuable wisdom for Buddhist practitioners. However, for most people Siddham literature is hard to understand, and they are especially discouraged from reading the charts regarding Chinese historical phonology. This paper mainly deals with some important technical terms found in Siddham literature, and provides a detailed illustration and explanation. Our aim is to let people be familiar with Siddham literature, and accurately grasp the contents. Section II briefly introduces the designing concepts of rhyme tables and their basic structures, and explains some of the commonly used terms, such as initials, voicing, five places of articulation, rhymes and tones. Section III analyzes the charts related to Chinese historical phonology found in Siddhakośa《悉曇藏》and Xitan Lunlüe Tuchao《悉曇輪略圖抄》. Section IV is the conclusion.
