To effectively evaluate the aging and moisture status of high-voltage bushings, a method for evaluating the insulation status of high-voltage bushings is proposed. This article analyzes the time-domain dielectric properties of oil-paper composite insulation in different aging states, and proposes the use of time-domain dielectric spectroscopy method to solve the equivalent circuit parameters of transformer oil-paper insulation under uncertain relaxation terms. In order to expand the application range of time-domain dielectric spectroscopy, Morlet wavelet is adopted to transform such signal and reduce background interference in high-frequency current. In the simulation section, a simulation model of high-voltage bushing oil-paper insulation structure is established. By analyzing the relaxation process of oil-water mixture, the insulation status of high-voltage bushings with different degrees of aging is tested. The experimental results show that time-domain dielectric spectroscopy analysis based on wavelet transform can acquire overall spectral information reflecting physical properties, which can be used for insulation detection and condition evaluation of oil-paper high-voltage bushings.