Abstract: The imperial edicts in early period of Tang Dynasty were "kings' speeches" of emperors at that time,they were released in the governance process,and they were political documents with the highest authority. These imperial edicts related to the historical facts,the politics,economicy,military affairs,law,diplomacy,education,culture,etc. at that time,they belongs to the first - hand information with Datang Venture Life Note,Tang Taizong Record and other historical books,their historical value is very high,and can make up the the palace of history books written in biographical style. Even those imperial edicts which were aimed at promoting a emperor's moral conduct,such as the emperor's enthronement,changing the title of a reign,worshiping heaven,grand ceremony on mountain top,etc. can provide a lot of valuable clues for us to investigate the historical facts of the time. This article will seek the truth of Li Shimin killing his brothers to seize power and Li Yuan forced to give up the throne through imperial edicts from June to September in the ninth year of Tang Wude mainly from the perspectives of the literature and history.