While only 813 volumes of the 22,000-volume Yongle Da Dian have survived. Fortunately, the Yongle Da Dian Catalogue (《永樂大典目录》)preserves the complete rhyme system of the Da Dian and provides a glimpse of the entire Da Dian. The catalog is from the "Lian Gyun Yi Cong Shu"(《连筠簃丛书》) published during the Daoguang period, and there is also a Qing copy containing the "Yongle Da Dian Catalogue" in 60 volumes, Yongle Dadian Zongyun Gekuo (《永乐大典韵总歌括》) (one volume) and Yongle Dadian Yunzong (《永乐大典韵总》) (four volumes), which can supplement the Yongle Dadian Zongyun Gekuo (《永乐大典韵总歌括》) andYongle Dadian Yunzong (《永乐大典韵总》)in the "Lian Gyun Yi Cong Shu". In this paper, we analyze the special phenomenon of "empty space and blackened" rhyming characters in the Yongle Da Dian Catalogue with the help of these related materials, investigate their original appearance and deduce their causes, so as to complement the rhyming character system of the Yongle Da Dian.