The invention relates to electric conduction polymer and a synthesis method thereof and an electroactive electrode with a surface covered with the electric conduction polymer. In the synthesis method for the electric conduction polymer, polybasic acid is used as a doping agent and a cross-linking agent, so that a monomer is polymerized to obtain electric conduction polymer hydrogel, wherein the monomer is at least one of pyrrole or a derivative of the pyrrole, thiophene or a derivative of the thiophene, phenylamine or a derivative of the phenylamine; and the acid group of the polybasic acid comprises a phosphate group or polybasic acid of which each molecule comprises more than two acid groups selected from at least one of a sulfonic acid group, nitroxyl or a carboxylic acid group and which has the molecular weight of less than or equal to 800. The molar ratio of the mole number of the acid group contained in the polybasic acid to the mole number of an electric conduction polymer monomer is preferably 1:12-12:1. The electric conduction polymer obtained by the synthesis method is covered by the surface of the electroactive electrode. The electric conduction polymer has a simple preparation method, and other impurities are not required to be led into the electric conduction polymer. The prepared electric conduction polymer hydrogel has high ionic conductivity, super hydrophilicity and high biological compatibility.