The harmonic series is the common physical basis of the melodic composition of all nationalities in the world,while the special rules of melody and melodic method of each nationality reflect their specific cultural and historical choices,which are embodied in the tonal structure and scale forms.Chinese traditional music has formed a simple, yet colorful modal scale system in the process of a long historical development which is based on the pentatonic scale and forms the hexatonic, septatonic and even enneatonic(also called nonatonic)scales by means of bianfan (变凡),and various neutral tonal modes are formed through the “transition”of prime numbers 11 and 13.Based on the theory of the mode system of the circle of fifth modulation and using the fifth chain as an analytical tool,the article transforms the theoretical discourse in ancient literature and terms in folk music practice into modern music theory concepts,and it analyses the material properties and modal structural force hidden in the underlying melody,thus showing the unique and rich modal scale characteristics of China's traditional music.Consequently,the article provides invaluable information of an inexhaustible traditional source for applications of the contemporary musical creation of Chineseness.