the present invention provides a conducting polymer , a synthesis method thereof , and an electroactive electrode covered with the said conducting polymer . the conducting polymer is synthesized as follows : use the polybasic acid as dopant and crosslinking agent , and polymerize monomers into conducting polymer hydrogel . the monomers are selected one or more from pyrrole or its derivatives , thiophene or its derivatives , aniline or its derivatives . the acid group of the polybasic acid contains phosphate or polybasic acid which contains at least two substituents per molecule selected from sulfate , nitrate or carboxylic in which the molecular weight of at least one acid group is no more than 800 . the mole ratio of the acid group in polybasic acid to monomers of the conducting polymer is 1 : 12 - 12 : 1 . the preparation applied in the invention is simple , and need not to import any impurity . the conducting polymer hydrogel has high ionic conductivity , super hydrophilicity , and good biocompatibility .