Herein, 1,3,6,8-pyrenetetrasulfonic acid (PTSA) functionalized Pt nanocomposites were synthesized and characterized by UV/vis, X-ray photoelectron spectroscopic (XPS), FTIR, TEM, and XRD methods. Pyrenetetrasulfonic acid was not only used as the stabilizer to prevent agglomeration of Pt nanoparticles but also served as the light-harvesting photosensitizer, absorbing irradiating light and transferring photoexited electrons to the platinum nanoparticles. The occurrence of the photoinduced electron transfer process was confirmed by the combination of time-resolved fluorescence and photoelectrochemical spectral measurements. Photocatalytic results showed that PTSA functionalized Pt nanocomposites could be used as stable photocatalysts for photoinducing H2 evolution. At the optimal reaction conditions (nPt:nPTSA=100, pH 3), enhanced amounts of hydrogen were evolved from the system under UV/vis irradiation in the absence of an electron mediator. The corresponding amount of hydrogen evolution was 125.1 μmol for 12 h exposure to UV/vis irradiation, and the apparent quantum efficiency at a wavelength of λ=365 nm was 11.5 %.