Vibration power flow and vibration intensity in general would be described by its propagating components and the near field components. Energy is transmitted by propagating waves, and no energy is transmitted by decaying waves. Near field effects are insignificant away from boundaries and sources, where only propagating waves exist. Under general field conditions, both near field and far field are considered. Finite difference approximations are often used for most estimation techniques. Using finite difference, the structural intensity or vibration intensity could be obtained either by a direct method where the vibration intensity is directly computed from the output field signals of sensors (velocity or acceleration); or by the wave decomposition method where vibration intensity is calculated from the solution of the bending wave equation. A complete solution is not generally available for plates. In this paper, theoretical flexural wave powers in naturally orthotropic plates are formulated using a finite difference approximation in the frequency domain under general field conditions.