The electromagnetic field is quantized in absorbing and dispersive dielectrics by Green's function method, and the quantum theory of the optical field is investigated one-dimensional system consisted of three-layered absorbing and dispersive dielectrics. The power spectrum of quantum fluctuations of the optical field in the dispersion and absorption dielectrics cavity is given by the fluctuation-dissipation theorem, and the effect of the dispersive and absorbing character of the dielectrics on the workability of an optical system is discussed by numerical caculation. The result shows that the working state of a system is connected with the frequency of the optical field. Absorbing and dispersive character of the dielectrics in every area influences not only the power spectrum of the electric field fluctuation of its ambient region, but also the other side's. There is an important meaning for exploring the pratical applications of the complicated dielectric distribution and structural system in optical communication, modern optic-engineering and microwave technology in the result.