The vocabulary genres of Chinese characters are very abundant, among which, the most typical one is idiom. Four-character idioms convey rich content with compact and settled structure style which can be one meaning, one story or one literary quotation. Ancient level and oblique tones belong to the range of ancient tradition phonology. Modern level and oblique tones is corresponding to ancient ones, which is in the modern Chinese phonetic symbols. The researches on ancient and modern level and oblique tones are both very abundant, but the evolution process from ancient level and oblique tones to modern ones are still scattered, less standard, and unsystematic. This paper attempted to study on this researching blank and selected the idioms with rhythmic features in modern Chinese. It will deepen the knowledge about traditional phonology and modern phonetics, then provide effective references to the progressive research of phonology.