The utility model discloses a capacitor, comprising a core, the core comprises a cathode foil, an anode foil and an electrolytic paper, the core is immersed with an electrolyte, and a conductive filmis arranged in the core; one end of the wire is connected with the core, and the other end of the wire is suspended; and the core is arranged in the shell. According to the capacitor provided by the utility model, the wound capacitor core is immersed in the polymer turbid liquid, so that a high-conductivity polymer film can be formed inside the core after the core is dried, and low impedance of the capacitor is realized; and meanwhile, the capacitor with the formed polymer film is immersed into the electrolyte to repair the oxide film of the anode aluminum foil, so that the capacitor has a very low ESR value and can bear higher ripple current. Thus, according to the capacitor and the preparation method thereof, the low impedance of the capacitor can be ensured, and the capacitor has a relatively low ESR value, so that the capacitor has relatively high comprehensive performance.