Abstract: "Buddhist Songs", which are the perfect combination of Buddhism and poetry, are unique in the history of Japanese literature. They originated in the Nara period, flourished in the Heian period, and matured in the Kamakura period. They are not only the wonders in the history of Japanese literature, but also play an important role in the history of Japanese Buddhism. The main reasons why "Buddhist Songs" flourished in the Heian era are as follows: (1)the prosperity of Buddhism provided necessary conditions for the creation of "Buddhist Songs"; (2)"the view of wild words and flowery expressions" cleared the way for the prosperity of "Buddhist Songs"; (3)the monastic reclusive singers became the creative subject of "Buddhist Songs"; (4)the resurgence of Japanese Waka and the development of its theory enriched the creation techniques of "Buddhist Songs".