The invention relates to a method for assessing an insulation state of oil 
paper based on characteristic quantity of 
frequency domain dielectric spectroscopy. The method comprises following steps: utilizing a 
linear medium response 
equivalent circuit to simulate polarization characteristics of the insulation state of oil paper for a 
transformer and setting up the relationship between 
linear medium response 
equivalent circuit parameters, frequency-domain characterization complex 
capacitance and 
dielectric loss factors; then, utilizing complex capacitances with 
high frequency bands and a parametric 
equivalent circuit model for 
dielectric loss characteristic quantity and finally, integrating 
dielectric loss curves with 
low frequency bands at prediction sections, wherein the range of frequency bands in a 
dielectric loss frequency domain is equally divided into n frequency points (n larger than or equal to 1), n frequency points correspond to n 
dielectric loss integral value and n frequencies and corresponding dielectric loss integral value are fitted to a function curve. The method for assessing an insulation state of oil 
paper based on characteristic quantity of 
frequency domain dielectric spectroscopy has following beneficial effects: in order to obtain much more insulation information carried by dielectric loss factors within the limited 
measurement frequency domain, integrals of dielectric loss factors are utilized in the predicted low-frequency section as characteristic parameters for assessment of insulation state; and dielectric loss integral value within the low-frequency stage obtained by calculations is utilized for determining the insulation aging state of oil paper.