Since Buddhism came to China in Han dynasty, its influence has deeply imprinted in every aspect of Chinese culture including literature, philosophy, and poetry in particularly has formed a trend of discussing it by Zen gradually. Being very proficient in Confucianism, Buddhism and Daoism, the Buddhist monks in the Six Dynasty were talented literary men of the time. During Tang Dynasty, there were many monks engaging in poetry writing and even formed a so-called “group of poem-monks.” Through examining the Buddhist monks’ literary works in Tang and Five Dynasties, this article aims to discuss their “rules of poetry” and investigate them with the following five categories: “phonology”, “the antithesis theory”, “the system theory”, “the creation theory” and “the style theory.” Their contributions towards poetic include: “to help to form the Tang poem system by inheriting Six Dynasties rules of phonology and antithesis”, “ to enlarge poem connotation and deepen poetry aesthetics”, “to document the massive poetic compositions of both the Buddhist monks and the laymen and set the poetry tradition up”, and “to affect the descendant rules of poetry, and form the trend of discussing the poem by Zen.” With illustrating these above effects, this article highlights the Buddhist monks’ contribution to poetics in Tang Dynasty.