In the study the questions of high-frequency heating were considered. The research was devot-ed to the nonuniformity of heating. The main rea-son of nonuniformity was wave nature of electro-magnetic field distribution in material. Nonuniformity increases with the increase of frequency and di-mensions of material. This problem is especially actual for high-frequency drying kilns because the length of loading can reach 8 m. Calculations of distribution of electric field strength were made at different frequencies to demonstrate the non-uniformity of the field. One-dimensional distribution was considered. Timber was chosen as dielectric. Calculations were carried out by 3 methods of mathematical description of wave phenomena. The first method was based on the system of Maxwell's equations and after a number of mathematical op-erations was transformed to a cosinusoidal view. The second method described the distribution of the electromagnetic field in the multilayered materi-al. Given method was offered by the authors and included Helmholtz's wave equation and boundary conditions of symmetry on free end of capacitor and Newton's boundary condition in the point of connection of the current distributor. Earlier ob-tained experimental data of voltage distribution on the length of working capacitor electrodes were given to check the accuracy of considered mathe-matical models. It was concluded that the first method was the least exact drawn on the analysis of calculated and experimental results. It was ex-plained by the neglect of the coefficient of attenua-tion which had essential value for damp timber. The second method was more exact, but as well as the first one, introduced additional error in voltage node. The maximum agreement with experimental results was provided by the model offered by the authors in the case of different ratios of wavelength and length of loading.