歷史研究最大的特性是「變」，觀察「質變」與「量變」，從而窺見古今歷史的發展與轉變。 唐代是中國史上一個重要的轉捩點，或如日本學者所言的「唐宋變革期」，或為劃分中古與近世的關鍵時代。無論如何，人口的分布、政區的劃分、財稅的收入與人才的比重等變化，多形成於安史之亂後，明顯的表現在經濟、社會與文化重心的南移。此一重心的南移，乃先由人口的遷徙所造成，繼而影響政區、稅收與文化之變動。因之，唐代人口的升降與變化，乃為古史研究之重要一環。 唐代人口研究主要來自兩唐書、《唐會要》、《唐六典》等傳統史籍，由於這些史籍在傳鈔過程中不免魯魚亥豕，數字容易造成千、萬以上的差距，如此一來將造成研究上的困擾。本文嘗試透過全國人口數字的對比，進而討論史籍傳鈔之諸問題，察知唐代全國人口數字問題之一二，日後或可藉此可再進一步討論唐代不同時期之各區人口分布，繼而申論人口升降與流動等諸問題。

Changing is one of the distinctive features in historical study, which people can see the history development and transformation through. Tang dynasty is the turning point between the medieval age and Modern age in Chinese history. After the An-Shih rebellion, the changes of demographic shift and tax incomes reflect on social 、economic and culture center south-toward shift. Therefore, review the Tang population issues helps to see the changes. Demographic records originate in ancient history records. The research of the population counts in Tang Dynasty, which comes from Shin-Tang-Shu, Jiu-Tang-Shu, Tang-Hui-Yao and Tang-Liu-Dian etc. However, there used to some mistakes appeared in historical resources transcription, which may increase the historical study difficulty. Therefore, this Article attempts to review the demographic records in historical resources.