Aiming at the limitations of the extended Debye circuit in the diagnosis of oil paper insulation aging, an improved hybrid equivalent circuit is proposed to characterize the polarization response characteristics of oil paper insulation media. The interface polarization branch is added to the extended Debye model to characterize the interface reaction between complex media. The characteristic parameters are solved using particle swarm optimization algorithm and combined with on-site testing to verify the reliability and conformity of the hybrid circuit, Simulate and analyze the impact of parameter changes in hybrid equivalent circuits on the polarization spectrum of the recovery voltage. The research results indicate that with insulation aging becomes more severe, hybrid circuits are closer to on-site measured data compared to extended Debye circuits; The time constant and resistance value will decrease, while the capacitance value will increase; The changes in small time constant, medium time constant, and large time constant correspond to the front, middle, and terminal parts of the recovery voltage polarization spectrum, respectively. This provides a more accurate analysis basis for evaluating the aging status of transformer oil paper insulation, and has certain reference and application value.