Different from the traditional treatment, we use the third-order tensor κ(2)jkl to describe the optical activity and take the corresponding polarization as a perturbation, and directly derive a wave coupling equation for the phenomenon from Maxwell's equations. The analytic solution of the coupling equation, which involves the results from the previous macroscopic theory of optical activity, describing the propagation of monochromatic light in arbitrary polarization state traveling in any direction in an optical active crystal belonging to any point group, is given in this paper. Finally, as an application of this theory, the influence of the wave-vector mismatch on the optical rotation in quartz crystal is studied in detail by analyzing the polarization state of the output light.