This paper applies probability and statistical analysis to the rime system in Huilin's Yiqie Jing Yingyi. It is found that the two chongniu (rime doublet) categories A and B are clearly differentiated, and for the most part are kept distinct. However, some distinct characteristics emerge when the rime system of Yiqie Jing Yingyi is compared with that of Qieyun. Chongniu category A is closely related to the fourth-grade rimes, while category B is closely related to the ordinary third grade rimes. These two categories can be differentiated through their upper and lower fanqie characters. An overall correspondence between them and the sibilant and dental initials is maintained: The initials yun, lai and those in the zhuang and zhi groups tend to pair with category B rimes, while the initials yi, ri and those in the zhang and jing groups tend to pair with category A rimes, but initials in the zhang and ri groups show traces of switching from category A to category B. The chongniu distinction lies within the medial elements of the rimes.