目前，大多数学者都意识到需求演化的重要性，然而依然缺乏有效的方法指导需求演化。反射式需求规约通过描述支持OWLS需求规约演化的元信息，并支持以合理的方式使用这些元信息，实现OWLS需求规约的演化。本文提出了一种基于π演算的反射式需求规约演化模型，使得反射式需求规约的演化能够以一种正确的方式实现。针对OWLS需求规约的特点，给出了OWLS需求规约的π演算描述方法；使用高阶π演算的进程传递机制，描述了支持演化的反射式需求规约；给出了反射式需求规约演化正确性的推理与验证方法。同时，我们采用交通出行的例子论证了本文的观点。

At present, most scholars know the importance of requirements evolution, but still lack efficient methods to guide. According to the problems mentioned above, this paper proposes an approach which supports the OWLS requirements specification evolution. By using the meta information of OWLS requirements specification，we can finish the OWLS requirements specification evolution. We propose a reflective requirements specification model based on πcalculus. For the OWLS characteristics, the OWLS requirements specification description method based on πcalculus is given. Using the processpassing mechanism in highorder πcalculus, the evolvement process of requirements specification can be specified. A reasoning and verification method is given for the correctness of reflective requirements specification evolution. At the same time, we use the  traffic traveling examples to demonstrate this argumentation.