”Coda” is a concept of music verse, a proper noun of Qu. It refers to a special stop-ending Qu of a suite. The Coda must be compatible with the meaning and the plots of Qu; trending to the climax or a calm ending to the most splendid dramaticeffect of the suite.The main key of the suite makes the music and plots difference. The quick music ends with slow melody; and the slow melody ends with quick one. We know the importance of the ending music-Coda.There is still so little study on the coda of Qupai presently. This article is goingto explore the main key, phrase rule, character rule, and the rhyme to rearrange the structure of music form and phenomenon; and so that to establish the fundamental theory of Qu.