Based on the framework of the Qièyùn (切韻) system, this paper explores phonological distinctions between Grade III and Grade IV of the Shān Shè (山攝) rhyme group, namely the Xiān (仙) and Xiān (先) rhyme, in Modern Xiang . Whether the Xiān (仙)/Xiān (先) distinction exists or not in modern Xiang dialects is still under debate. These different views constitute the primary research motivation of this paper. This paper concludes that:1. The Xiān (仙)/Xiān (先) distinction is indeed preserved in Modern Xiang, and the phonological contrast occurs after the initials of the Jing (精) series of Middle Chinese. 2. According to the phonetic representation in Modern Xiang, Xiān (仙) could be reconstructed as *-iɑn and Xiān (先) as *-ian. 3. By comparing with other proto dialects, we reconstruct the contrast of *- iɑn and *-ian in the old Jiangdong dialect of the Six Dynasties, which establishes the close relationship between Xiang and Jiangdong dialect in history.