A new substrate,aligned Ag nanowires decorated with silver nanoparticle composite structure (AgNWs@AgNPs),was fabricated to investigate metalenhanced fluorescence (MEF) and its mechanism.The new composite structure was fabricated via a three-phase interface assembly method followed by SnCl2 sensitization and AgNO3 reduction process.The size and distribution of the nanoparticles on silver nanowires increased with the sensitization and reduction cycles.The formation of AgNPs on the surfaces of AgNWs was confirmed by multiple characterization methods including scanning electron microscopy (SEM),transmission electron microscope (TEM),atomic force microscopy (AFM) and X-ray diffraction (XRD).The results show that the fluorescence intensity of the poly(3-hexylthiophene) (P3HT) on the composite structure was greatly enhanced compared with that on bare glass substrate,and the intensity increased with the increase in particle sizes and density.The mechanism was based on the increase in excitation rate and the radiation decay rate.The new type of substrate could serve as a good and efficient MEF substrate for high-performance fluorescence-based devices.