Abstract: The converter transformer is subjected to multiple factors such as the actions of electricity, heat and vibration during operation, and its oil-paper insulation aging process is complicated. How to evaluate the insulation aging characteristics of converter transformers under the combined action of multiple factors is a key operation and maintenance problem that needs to be solved urgently. In this paper, the time-domain dielectric response technology is used to obtain oil-paper insulation samples with different aging degrees through accelerated multi-factor aging tests, and the polarization and depolarization current curves of oil-paper insulation models with different aging degrees are measured. Moreover, the changes of electrical conduction current with time are calculated according to the test results, among which the absorption current that decays exponentially is extracted. Secondly, the absorbed current is integrated to calculate the parameter value of the absorbed charge, the relationship between the steady-state absorbed charge and the degree of polymerization is established, and the insulation state is classified by the relative growth rate of the absorbed charge. Finally, the linear straight spectrum line is drawn by the logarithmic processing of the absorbed current, and the absolute value of the slope of the straight spectrum line is extracted as the characteristic quantity to evaluate the aging state of oil-paper insulation, which provides a theoretical basis for the evaluation of the aging state of the converter transformer insulation.