The structural intensity technique using cross-spectral densities is used to estimate the quasi-longitudinal wave power in rectangular and trapezoidal corrugated plates in the frequency domain. The two-point transducer method for in-plane power in naturally orthotropic plate, whose thickness is uniform, is used for measuring in-plane vibration power transmission of these plates. The method of elastic equivalence is used to facilitate power flow estimation. It is also necessary to re-model the trapezoidal corrugated plate to rectangular corrugated plate so as to apply the method of elastic equivalence. An isotropic plate is also used for this measurement. Measured in-plane power flow from corrugated plates is compared to that from isotropic plate. The effects of in-plane stiffness on vibration power flow are also investigated. In-plane power flow is observed to reduce gradually as the frequency increases. The effects of in-plane stiffness of the plates on quasi-longitudinal wave power are insignificant in the frequency range of interest. Some negative values of power are also observed at some frequencies at lower range.