A novel ab-initio theory has been investigated to obtain the microwave attenuation in high temperature superconductors by using the quantum dynamical approach of double-time temperature-dependent electron Green’s functions technique. First of all, we have calculated the expressions for electron density of state (EDOS) via an almost complete Hamiltonian which includes the contributions due to the unperturbed phonons and electrons, anharmonic phonon fields, localized phonon fields, and that of electron–phonon interaction. After obtaining expressions of microwave attenuation in high temperature superconductors, it is observed that the EDOS plays a vital role in the microwave attenuation. We have seen that the microwave attenuation depends chiefly on temperature, electron–phonon coupling, concentration of phonon, etc. The results show good agreement with experimental observations.