In this paper, we present a convenient and universal strategy to sequentially assemble titania (TiO2) nanorods and polyaniline (PANI) nanoparticles on the Si wafers through hydrothermal synthesis and chemical oxidation. On the one hand, the composite coatings (PANI/TiO2/Si) with hierarchical structures reduced the reflectivity to less than 5 % at the wavelengths from 200 to 2500 nm, namely increasing the absorption efficiency of incident light. On the other hand, the double P-N heterojunctions that the composite coatings developed could suppress the recombination of photogenerated carriers, namely enhancing utilization efficiency of absorbed light. The photocurrent density of PANI/TiO2/Si was above two times higher than that of TiO2/Si at 1.5 V of positive potentials. The application of such coatings in the photocatalysis area, which are fabricated with this method, is thus straightforward.