Ki no Tsurayuki provides more waka poems than anybody else to the volumes of sandaishū, consisting of Kokin Wakashū, Gosen Wakashū, and Shūi Wakashū. This presentation aims to facilitate a better understanding towards the role Tsurayuki has fulfilled in mid-Heian literature, especially by focusing on kotobagaki.In the first part of the “Spring” volume of Kokin Wakashū, 11 out of 68 waka compiled are by Tsurayuki. It must be noted that all of those waka are supplemented by kotobagaki. Especially, three waka are labeled as Tsurayuki’s composition answering emperor’s direct request; such kotobagaki can only be seen with Tsurayuki’s waka. In the second part of the volume, 13 out of 66 waka are by Tsurayuki. Here, kotobagaki clarifies that some of the verses were taken from “Kanpyo Ontoki Kisaki no Miya Uta-Awase”, a poetry contest that can very well be considered a preparation of Kokin Wakashū, and also from“ Teiji-in Uta-Awase”, which was hosted after the original compilation of Kokin Wakashū.Next, if we take a look at some of the kotobagaki in Gosen Wakashū, we can surmise that it was among the editors’ design to historize Tsurayuki. For example, in three parts of the “Spring” volume, we can see that Tsurayuki once enjoyed friendships with his colleague Mibu no Tadamine and his patron Fujiwara no Kanesuke, but eventually became reclusive, and died alone.In Shūi Wakashū, on the other hand, it seems that stronger attention is paid to glorify Tsurayuki with stronger authority. For example, the nine waka in the“ Spring” volume are not only from the past uta-awase, but are also the waka used for festive occasions concerning high-ranking aristocrats, such as Fujiwara no Yoshiyo, Fujiwara no Atsutada, and Princess Kōshi.Tsurayuki has evidently served a great purpose in the building of poetic canon during the Heian Period. It seems that his importance is emphasized by each of the poetic anthologies as well, but in slightly varying fashions.