The characteristics of the mainstream literary forms of the Song Dynasty included: - Poetry: The Song Dynasty was the golden age of Chinese poetry development. Poetry had great innovation and development in literary form and content. In the Song Dynasty, poetry was created in a wide variety of forms, including five-character quatrains, seven-character quatrains, Ci, Qu, etc. - Prose: Prose was the mainstream form of literature in the Song Dynasty. It was an important tool to express ideas and reflect society. Prose was unique in its emphasis on true feelings, free form, and concise language. Song Dynasty prose expressing emotions formed a unique literary style. - Fictions: Fictions were an important form of literature in the Song Dynasty. They were an important tool to express people's thoughts and emotions and reflect social reality. The novels of the Song Dynasty were full of twists and turns in the plot, profound character descriptions, and concise language. The reasons for the prosperity of novels in the Song Dynasty were mainly as follows: first, the market demand, second, the innovation of novel creation methods, and third, the support of literary criticism. The main reasons for the prosperity of the Song Dynasty's literary form were as follows: - The Song Dynasty was a period of economic prosperity in China, and literary creation was closely related to social needs. - Diverse culture: During the Song Dynasty, there was a trend of development in the field of culture and art, and literary creation also showed a diverse situation. - Literature criticism: The Song Dynasty's literary criticism system was complete, and literary critics carried out in-depth analysis and evaluation of literary works, which promoted the development of literature. - Market demand: The large number of novels, essays and other literary works in the Song Dynasty promoted the prosperity of literary creation.