悉曇真言在佛教的修行中，具有相當重要的地位。所謂「一字一法門，一法門可成正果」。因此悉曇的知識對於佛教修行人而言，是一種寶貴的智慧。然而，悉曇文獻對一般人而言是艱澀難懂的，令人對之卻步。本文主要針對悉曇文獻中，所見的一些漢語音韻學上的觀念，加以說明解釋；讓大家在閱讀悉曇資料時，更能精確地掌握內容。第二節先簡單的介紹韻圖的概念和其基本結構，並解釋一些常用的術語，如字母、聲母、聲紐、清濁、五音、韻母和四聲；第三節則針對悉曇文獻中有關漢語聲韻學的一些圖表加以分析說明，包括《悉曇藏》卷二有關四聲的漢字表，和《悉曇輪略圖抄》中〈聲字實相事〉、〈四聲事〉、〈八聲事〉、〈反切事〉、〈聲韻事〉和〈弄紐事〉的一些圖表。第四節是本文之總結。

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.