We report in this paper a dual catalytic effect of water soluble soft coordination supramolecular polymers (SCSPs) based on Fe3+ and a bis-ligand. Upon assembling the Fe(III)-SCSPs onto electrodes via layer-by-layer technique, the electroactive films may lower the half-wave potential for all the tested molecules and enhance the current for neutral or oppositely charged electroactive species. The decrease of the half-wave potential was attributed to the mediation of the Fe(III)-SCSPs in electron transferring, whereas the enhancement of current is a consequence of accumulation of electrons in the films. We verified that this dual catalytic effect is general to neutral and cationic redox active molecules, and can be used to detect hydrogen peroxide owing to the significant enlargement of catalytic current. Our results proved that the water soluble soft coordination supramolecular polymers containing metal centers are indeed a novel class of advanced catalytic materials, which may open a new vista on the design and study of materials of this class.