本文提出用微分法确定简单一级反应的速率常数。该法的特点是不用测定无限长时间的物理量。文章给出了方法的原理和确定步骤，并进行了误差分析。在一些具体实例的讨论中和Ｇｕｇｇｅｎｈｅｉｍ法作了比较。 In this paper, differential method is used to determine the rate constant of simple first order reaction. The law is characterized by not having to measure the physical quantity for an indefinite length of time. The article gives the principle of the method and the determination step, and carries on the error analysis. In the discussion of some specific examples, the Guggenheim method is compared.