本文主要在了解唐人借貸的計息方式，觀察官、民借貸制率的變動，以及影響利率變動的因素。唐代因官方實施各種本錢的放貸，故詳於訂定官本利率，亦時而兼及私舉質，但該種法定利率能否因應政輕情勢而隨宜調整，能否切合資金供需狀況而通行於全國，並且能否反映城鄉、物種之特色，能否該人民免於高利貸之剝削，都應詳加推究。本文從傳統文獻與敦煌吐魯番文書中的民間約定利率，比較其與官方法定利率的關係，說明當時為何存在官、民兩套利率體率，並進而分析影響利率走勢之主、客觀因素。

　　　　　This article aims to observe the long trends of interest rate during the T'ang dynasty and to analyze whether the interest rate in the civic circles was the same as the legal one. Furthermore, the author hopes to pursuit the causes that influenced the changes in interest rate. It was quite possible that due to policy consideration the administration body chose to suppress the official interest rate. However, the interest rate for pers onal contracts was usually higher than the official rate because of unhealthy financial constitutions and insufficient social capital resources. Base on loan situations of Hsi-chou and Sha-chou described in Tun-huang and Turfan documents, one can infer how impossible it was to have a standard interest rate at anytime in T'ang. Adjustment of interest rate was made to meet the required conditions with regard to political stability, objects for loan, geological areas, personal credibility and unexpected elements. That is why the problem of interest rate was not as simple as officially anticipated.