在中國文學（史）、文學思想（史）的研究過程中，我們往往仰賴正史（尤其是文學類傳的資料）做為論據。事實上，一部史書的完成，乃是史家面對過去的歷史事件，以及歷史事件所遺留下來的史料，運用其才智學養、情感想像等，逐一檢擇耙理、綰合聯繫而成。史家的一切觀點，有來自於己身的個殊經驗，也有出自於社會的時代氛圍，乃為複雜的人文現象。對正史文學類傳進行研究，應有助於我們反省某一時代解讀另一時代文學史的狀況，並便於我們接近被解讀時代的樣貌。
本文擬以兩《唐書》文學類傳為例，說明歷史圖像與文學評價疊合的狀況。為求討論方便，先自兩篇傳序共同涉及的「時變」觀念展開，再通過特定作家的傳文記錄，指出兩書在歷史圖像與文學評價疊合上的差異，進而彰顯文學類傳的兩重主觀性。

Actually, investigators in ancient China dedicate themselves to their works as various kinds of accomplishments of historical records. Study on history presented in a series of biographies benefits us to introspect one dynasty to decipher another. In this paper, I would take the literary bibliographies of the two “Tang Books” for example to describe the conditions about the overlaps between historical images and literary evaluations. Firstly, for convenient, I spread out the paper by temporal alteration which the two “Tang Books” involve in. Secondly, through specific writers’ articles to point out the differences of historical images and literary evaluations between the two books to manifest the duel-subjectivism of literary bibliography.