本文通过分析罗马法债的定义及萨维尼等法学家关于债的本质的观点,得出的结论债的本质在于债务人方面的行为必要性。进而可以说债之起点不是债权而在债务。合同之债的起点在于设定义务关系,其本质就是一种义务关系,申言之,债之本质在于给付行为,给付行为是债之利益得以实现的决定性因素。 By analyzing the definition of roman law debt and the opinion of jurists such as Savigny on the nature of debt, this paper concludes that the essence of debt lies in the necessity of the behavior of the debtor. It can be said that the starting point of debt is not debt but debt. The starting point of the contract debt lies in the setting of the obligation relationship, which is essentially a kind of obligation relationship. The essence of the debt lies in the payment behavior, and the payment behavior is the decisive factor for the realization of the interest of the debt.