南朝宋、齊政權在統治蠻人的機構方面，除了繼承兩晉以來的蠻府制度外，更重要的是創造出屬於特殊政區的左郡左縣。劉宋初年，甫建立左郡左縣，至劉宋中期以前數量增多。其中，豫州左郡左縣的設置也與蠻府相配合，包括安蠻校尉府以及眾多的鎮蠻護軍府等，同時也增設許多新縣。這些與北魏的軍事競爭密切相關，使得劉宋政權極欲掌控當地蠻人，提供人力與物力上的支援，但曾遭到蠻人劇烈地反抗。與一般學界理解不同，本文特別強調左郡左縣在名稱上的調整。因此認為名稱上的變化，反映了左郡左縣在施行上的不穩定，置廢頻繁，改置、改隸屬皆常發生。此外，左郡左縣長官也不盡由蠻酋擔任。蕭齊以後，左郡左縣的設立逐漸擴散且增多。但到了蕭梁時期，隨著戰事的失利，許多邊境土地淪沒，左郡左縣也逐漸改為正郡正縣。這些制度的變化，既顯示南朝是不斷透過不同的管理方式統治蠻人，也說明南朝與蠻人之間的競爭並未如一般學界所認為，制度消失標示著蠻人漢化的成功，而是存在著複雜的歷史進程。

While the Southern Dynasties continued to use the special military regions for border peoples (man fu) inherited from the Jin dynasty, they also established a system of zuojun and zuoxian (commanderies and counties of the "left") to govern the Man ("barbarian") peoples residing along the Yangtze River basin. The Liu-Song dynasty established the zuo system, using it especially in the Yuzhou region, where these units were operated in combination with military regions to muster resources needed for war with the Northern Wei. The Man peoples rebelled fiercely under this policy. In contrast to existing research, this study pays close attention to changes in the names of these commanderies and counties, showing how these changes reflect instability in the zuo system. Additionally, it is shown that the heads of zuo localities were not always from the Man people. The zuo system was expanded in the Southern Qi dynasty, but came to an end under the Liang, when some zuo units were regularized, while others fell into enemy hands. The restructuring of the zuo system was a complex process, and we should not regard it merely as the result of the sinicization of the Man peoples.