Discussion and analysis on political cause to form poem's characteristic in early and middle Northern Song Dynasty

Early and middle Northern Song Dynasty is the key period to form poem's characteristic of Song Dynasty.In this period,political power brings unprecedented influence on the development trend of poem,mainly show as energetic rule-by-literature makes political group literary,ruler's intentional advocation induces the popularity of Bai Juyi's style and Xikun style,Qingli New Deal,Xining Reform and other political movements drive the poem creation upsurge,further promote the political tendency of poem.