The invention provides a capacitor core, and an electrolytic capacitor and a screening method thereof, relates to the technical field of electrolytic capacitors, and solves the technical problem thatan electrolytic capacitor is easy to break down when the circuit voltage fluctuates in the prior art. The capacitor core comprises a capacitor core body and an isolation layer. The capacitor core bodycomprises an anode layer and a cathode layer, and the isolation layer is located between the anode layer and the cathode layer; the isolation layer comprises at least four layers of superposed electrolytic paper, and/or the electrolytic paper is made of a pressure-resistant material. The electrolytic capacitor includes an electrolytic capacitor body and a capacitor core. The screening method comprises at least two steps of: aging treatment and anti-lightning voltage test for screening. The capacitor core, and the electrolytic capacitor and the screening method thereof can prevent the electrolytic capacitor from being broken down when the circuit voltage fluctuates.