Besides a very important status in the history of politics, as a sacred place of the Chinese Communist Party, Yan'an plays a very critical role in the construction and eradication of the history of poetry. A lot of poets as He Qifang, Bian Zhilin, Tian Jian, He Jingzhi, Guo Xiaochuan, Ai Qing and etc. who had different identities and different poetic backgrounds changed their styles of works after they entered Yan'an. By analyzing these style changes, this article shall explore how "Yan'an Rectification" and "Yan'an Speech" caused fatal influence on poetry creation in liberated areas. In order to make effective comparisons, this article moderately borrows the personality traits of a novelist named Xiao Jun to help explain some of the phenomena and issues.