Abstract: In order to explain the microscopic mechanism of oil-paper insulation material's dielectric response in a sufficiently wide frequency range in depth and comprehensively, the present study considers both the universal relaxation law and classical theoretical model in dielectric physics. By taking full advantage of the thermal characteristics of dielectric processes, barrier height, as an intrinsic parameter, the method was proved to be effective in establishing connection between frequency domain spectroscopy test and thermally stimulated current when observing same dielectric process in the two aspects. Further, with the correlation between the real and imaginary parts of complex permittivity curve as well as the first order partial differential equation of response spectrum data, a synthetical analysis that effectively reveals microscopic mechanisms of dielectric process in frequency domain is established. With this newly developed method, the results illustrate that in a relatively large temperature range, oil-paper's response curve is generated by independent dielectric processes which are, respectively, low frequency dispersion, conductance, electrode polarization, interfacial polarization and dipole polarization. These processes' generation mechanisms, function expressions and occurrence conditions are also clarified according to quantitative study. By revealing the charge carriers' motion law in relatively wide frequency band, the present study contributes to the theory explanation and application of frequency domain spectrum.