The purpose of this study is to review the valuable books of Buddhist literature published during the Goryeo period in the Yanching Library which is the East Asian Library of Harvard University in the United States, as well as to introduce the readers to the preservation status of ancient documents in the library and their academic values. Although there was already an annotated catalogue published by Gyeongin Munhwasa in 2005, after comparing the catalogue with the actual documents at the Yenching Library in 2019, there were considerable differences between the two. To preview those differences, first of all, there was an inconsistency in the catalogue with the actual contents due to an error made. Secondly, there were cases in which the book titles seen in the catalogue did not actually exist in the library. Third, it was not easy to understand the current status of the rare books in the Yenching Library because the contents explained in the annotated catalogue were too short. Therefore, this study is to examine and introduce when and what routes were taken to transfer those books to the Yanching Library—which is not covered in the catalogue—in addition to correcting and improving the existing version. There are some books that have been transferred directly from Korea, but interestingly, it is estimated that there are also valuable rare books that have been transferred directly from Japan to the US. To conclude, this study is to promote the value of ancient Korean literature to China in the future and ultimately to use it as a basis for comparative research on Buddhist literature related to Korea, China, and Japan.