Abstract: To further analyze and obtain the parameters which characterize the relaxation and conduction processes of the cross-linked polyethylene(XLPE) cables, thus to quantitatively evaluate the insulation status, we take the polarization current spectrum as the identified object, and introduce the Sparsity-promoting dynamic mode decomposition algorithm, which is used to identify the equivalent circuit parameters of the extended Debye model. First, we need to calculate the sparsity-promoting amplitude vector with the polarization current. Then, we can identify the number of branches of the extended Debye model, and utilize the non-zero elements of the vector corresponding to the dielectric response true mode. Finally, the parameter identification of the equivalent circuit branch components is realized. The results show that this method has higher identification accuracy than the conventional method. In addition, according to the features of the polarization/depolarization current measurement, compared with the depolarization current, the identified results of parameters utilizing the polarization current is more accurate and reliable. This viewpoint has also been verified by the simulation and experiment results in the study.