We propose a generalized Poynting vector model (GPVM) that can simultaneously calculate the spatial and spectral distributions of the electric field intensity, optical power flow, and optical absorption as well as the power dissipation spectrum for all optical modes of organic light-emitting diodes (OLEDs). The theoretical formulation of the GPVM with respect to the dipole orientation and light polarization is derived by combining the dipole source term and transfer matrix method as a function of the normalized in-plane wave vector u. In the GPVM, the theoretical expression of the spectral power density, derived from the time-averaged Poynting vector at the emission layer, proves to be identical to that presented by the currently-used point dipole model. In a bottom-emitting OLED, the electric field profiles of the waveguide (WG) and surface plasmon polariton (SPP) modes obtained by the GPVM are nearly same as those calculated by the boundary eigenvalue solver except the slight difference at the position of the dipole emitter, which only occurs in the case that the excitation efficiency of a WG or SPP mode is relatively small. Finally, two-dimensional plots of the internal optical power flow and optical absorption, providing physical and intuitive information on the internal emission process as well as the absorption loss of all the optical modes, are calculated as a function of the longitudinal position and normalized in-plane wave vector. Compared with the currently-used electromagnetic methods of the Green's function, dipole radiation, and point dipole models, the proposed GPVM has the advantage that it can provide all the spatial and spectral calculation results of the electric field intensity, optical power flow, and optical absorption with respect to the dipole orientation and light polarization, which are essential in the optical modeling and analysis of OLEDs.