The growth of electrical trees in cross-linked polyethylene, a cable insulation material, is the main cause of its insulation deterioration. In this paper, the self-similarity of electric field distribution is investigated based on the self-similarity feature contained in the geometrical structure of electrical trees. Firstly, the geometrical structure of the electrical tree is simulated based on the L-system, and the self-similarity characteristic of the electric field distribution in this model is investigated. Then, based on the real electrical tree model obtained from X-ray Computed Tomography (XCT) scanning and the coordinates of the skeletonized model, the main electrical tree structure is reconstructed in COMSOL simulation software, and its electric field distribution characteristic is investigated. Finally, the simulation results of the simulated structures of the L-system and real structures are compared to summarize the self-similarity characteristics of the electric field distribution in the electrical tree.