The application provides a conductive polymer, comprising a segment obtained by polymerizing a polymer monomer, wherein the polymer monomer comprises a compound represented by Formula I: wherein Y is selected from one of NH and S; R1 and R2 are independently selected from H, an optionally substituted linear or branched alkyl group, optionally substituted cycloalkyl group, optionally substituted aryl group, optionally substituted aralkyl group, optionally substituted alkoxy group or hydroxyl group, or an organic group containing at least one of a carboxyl group, sulfonic acid group and phosphate group, and at least one of R1 and R2 is an organic group containing at least one of carboxyl group, sulfonic acid group and phosphate group. Meanwhile, the application discloses a capacitor comprising the conductive polymer and a preparation method thereof. The conductive polymer provided by the application has a lower ESR and stable electrical performance.