HPM(History and Pedagogy of Mathematics) become an important issue to us now. Study on old Korean mathematics books were made recently. We study mathematics books in Kyujanggak in this article. Horng Wann-Sheng 洪萬生, an math. historian and a member of editorial board of Historia Mathematica, visited Kyujanggak, the royal library of Joseon Dynasty. After his visit, he published a paper, "The first visit to mathematics books in Kyujanggak 奎章閣收藏算書初訪"(2008 Kyujanggak 32, p. 283-293). In his paper, he also raised several research problems on the history of Korean mathematics. In this paper, we analyze his paper "The first visit to mathematics books in Kyujanggak" and give some answers to those raised problems on Korean mathematics. Also we correct some misunderstanding of Horng on some facts. Especially, we make it clear that the author of SinJungSanSul(New Arithmetics 新訂算術) was not Lee Sang-Seol(李相卨), whom Horng considered as the author, but Lee Gyo-Seung(李敎承) through the correct translation of its preface and an article about its copyright lawsuit. And we added some pathways how Chinese mathematics books were imported by Joseon. We introduce the case of Hong Dae-Yong(洪大容) in detail.