本文主要檢討過去學者對秦漢刑期的看法，並據江陵張家山漢簡〈二年律令〉、其他出土文獻及傳世文獻，從概念和實際存在的律令兩個層次，重新論誰漢文帝以前的秦漢刑罰已存在某種形式的有期刑。刑期制出現的背景十分複雜，今日已難以全面了解，但和春秋戰國以來綿延不斷的戰爭和人力需求應有關係。秦的法律體系是在百餘年戰爭中逐步形成的，是戰時體制下的產物。漢承秦制，因而也繼承了秦法律體系早已存在卻不及整頓的問題。其中兩大問題即刑期制和肉刑。漢文帝改革的意義並不在將過去的終身刑或不定期刑改為有期刑，而在使原本存在的有期刑常態化、體系化、固定化和全面化。

Based on the newly published legal texts unearthed at Zhangjia-shan (張家山), Jiangling (江陵), Hubei (湖北), this paper contends that a system of terms of servitude appeared in the Qin and Early Han China. The idea and system of terms of servitude took shape gradually in the periods of Spring and Autumn and Warring-States. The melting-down of the feudal system of ranks and the needs of manpower of the time contributed to its appearance. The main task in the legal reform of the Emperor Wen was not, as many scholars assert, to start a system of terms of servitude, but to make the existing forms more systematic.