In this paper, polymethyl methacrylate (PMMA) nanospheres were prepared by emulsion polymerization. The aniline was chemically oxidized and polymerized on the surface of nanospheres. Then eigenstate polyaniline coated polymethyl methacrylate (EB/PMMA) nanosphere composite electrode materials were prepared by dedoping. The structure and morphology of the electrode materials were characterized by infrared spectroscopy and scanning electron microscopy. The electrochemical properties of composite electrode materials with different contents of PMMA were tested in a three-electrode system. The results show that in the 0.5 mol/L H₂SO₄ electrolyte, when the current density is 3 mA/cm², the PMMA doping amount is 0.075 g, the specific capacitance of the EB/PMMA composite electrode material can reach 732 F/g, and the 2000 cycle retention rate is 82.5%. It is assembled into an asymmetric two-electrode system with activated carbon. In the H₂SO₄-KI composite electrolyte, the energy density can reach 104 Wh/kg.