The study of dialects's history is a comprehensive study of language and history, language and diversification, language and culture. As a starting point, "The study of the phonetics of modern south Hunan mandarin" is mainly on Chenzhou and Yongzhou mandarin. It studies their phonetic characteristics during the last years of the Ming Dynasty and in the middle of the Qing Dynasty, their relationship with history, diversification and culture, also it studies the laws of historical development that followed constantly for four centuries. Finally, the study investigates the principles of the development of modern south Hunan mandarin, and discusses the modern south Hunan mandarin from the historical perspective. Within the historical context, we should pay more attention to racial interaction and local culture.Summarizing the above two points, we will try to enrich and innovate the theory of dialect and rhyme.There are five chapters in the text.Zixue Yuanyuan by Yuan Zirang, which is a very valuable rhyme book, is an important literature to study the speech sound of modern south Hunan mandarin. In the first chapter, we proofread, examine and correct the theory of orthoepy and vulgar sound by employing literature textual research, and we come to the conclusion that vulgar sound system does reveal deeply the Chenzhou mandarin's characteristics in the last years of the Ming Dynasty, some of which still exist in modern southwest mandarin.In the second chapter, we study the Daialect from Fengsuzhi carefully, which is the part of Yongzhoufuzhi, and find out the phonetic characteristics of Yongzhou mandarin. After that, we can clearly explain the history of Yongzhou mandarin and recognize the south Hunan mandarin on a higher level than before.In the third chapter, our study reveals the characteristics of the south Hunan mandarin during the period of the Republic of China by studying the two reports about the local phonetics of south Hunan mandarin. What's more, this study is closer to the south Hunan mandarin during the period of the Republic of China.The fourth chapter summarizes three chapters before, it discusses the evolvement of the Chenzhou mandarin and Yongzhou mandarin by surveying the south Hunan mandarin's sound situation during the Ming and Manchu dynasties, the period of the Republic of China and modern. We find out that their development have continuity and comparability although they're different. We can sum up the evolvement of the south Hunan mandarin on principle.The fifth chapter is the radioactive research. It reveals that there are some other influences that effect the evolvement of the south Hunan mandarin, such as social changes, interracial and multiethnic fusion and cultural exchanges. Besides, these factors also influenced the mandarin and its idioms which are the main trend in south Hunan. In this sense, our research can reveal the historical linguistic influences in the evolvement of the south Hunan mandarin.