In this paper, through theoretical derivation, a functional relationship is revealed, demonstrating that the variation in time between objects in relative motion depends on both their relative velocity and the finite propagation speed of light. By applying the relationship of time change to the theory of classical mechanics, it can be concluded that the interaction force between objects are also related to the relative motion velocity. Due to the introduction of the speed of light in the formula of classical mechanical theory, the applicable scope of classical mechanics theory is effectively expanded, so that it is not only applicable to the calculation of low speed moving objects, but also to the calculation of high speed moving objects. Subsequently, through careful derivation within this new framework, several fundamental laws of classical electromagnetism were derived, the results of which strongly support the validity of the new functional relationship.