Abstarct: The laser-plasma interaction is an important field because of many applications, such as the fast ignition scheme of inertia confinement fusion, particle accelerator, coherent x/γ-ray sources and etc. The nonlinear effects are strongly important in such cases because of high laser intensity influences. On the other hand, many nonlinear phenomena in the interaction of a high-frequency electromagnetic wave with plasma are related to the ponderomotive force. In this work, considering the ponderomotive force and using the hydrodynamic equations, we have studied the high frecuency electromagnetic wave behavior in a collisionless unmagnetized non-isothermal plasma medium and the related curves are plotted. It is shown that the laser intensity has affected on the profiles of the electric and magnetic field also the electron density variations. We have continued our study about resonance absorption with considering the propagation of a high frequency P-polorized electromagnetic wave obliquely incident into underdense plasma. The optimum angle and the absorption rate for different density distributions were obtained. The elcteric and magnetic fields variations were plotted. It was shown that the linear, parabolic and exponential density distributions and the small-scale-length variations has affected the absorption peaks and the optimum angle.