In this paper, it clarifies different study theories for ”Yuefu Chuansheng”, by a senior scholar Xu Dachun, to grasp the quintessence of Xu's melody singing system, uncover the aesthetic implications of the theory and make clear for its position on melody singing theory history. The melody singing system mainly includes three main lines: (1) It takes ”Melody Saving” as purpose of ”to express tender feeling with the harmony of both article and melody ”as its guiding principle and establishes the melody singing theory basis of ”singing and writing are working together”; (2) It takes the melody singing structure of ”word-sentence-name-tune-feeling” to present the course of melody completely; (3) It takes ”oral method” as the detailed content of singing method, and ”heart, force, breath, position, shape and sound” as the six elements of oral operation to construct two principles of ”leading oral singing with the heart” and ”unifying the principle with the shape”. The theory has three kinds of contribution: (1) The interweaving, interaction and coordination of the three main lines make planar pattern of ”clear words, pure tune and correct rhythm” broken through since Wei Liangfu and become a meticulous and understanding stereo mode; (2) It transfers the rhyme singing method ”way of cutting is the way of singing” by Shen Chongsui into real melody singing and completes the structure at all levels in words and tune singing; (3) lt invents ”oral method” theory, which is analyzed precisely and discussed in detail. Traditional Kunqu Opera singing theory of Qianlong and Jiaqing eras is constructed completely in Xu's hands, and the ”word, sound, breath, rhythm and feeling” theory proposed by Yu Zhenfei inheriting his father Yu Suying's theory in moredern times is still all developed from the basic mode of Xu's structure.