This research conducted a comparative analysis between Ménggǔ Yùnlüè (cited in the MC rhyme set Zhī 支, Zhǐ 紙, and Zhì 寘 of Sa Seong Tong Hai) and Ménggǔ zìyùn in the British Museum. The result tells us the only three examples, zhī 祗, xī 醯 and zhí 埴, show differences in their reading pronunciations, although there are some significant differences between the two texts. Further research will be needed to clarify these differences, and it is expected that more systematic comparative analysis between Ménggǔ Yùnlüè cited in the rest of the rhymes of Sa Seong Tong Hai and Ménggǔ zìyùn will explain the correlation between the two texts.