In practical software development, requirements are usually changed over time due to various reasons. The phenomena of changing requirements are called requirements evolution. It is challenging for requirements engineers to verify and preserve correctness of the requirements in such an evolution. This paper aims to technically analyze the possibility to use a refinement mechanism of Event-B, a formal specification language, to preserve the correctness of requirements in the requirements evolution. By regarding one step of the refinement in Event-B as a step of the evolution, we mathematically prove that the refinement mechanism of Event-B preserves the correctness at every step. This leads to our conclusion that it is possible to use Event-B to help requirements engineers verify and preserve the correctness of requirements during the requirements evolution.