In order to effectively reduce nitro compounds in contaminate water and produce hydrogen from water, Ag/mpg-C₃N₄ nanocomposite particles are prepared by impregnation method, and 5-OH-ZnTPP is loaded on the surface of Ag/mpg-C₃N₄ to prepare Ag/5-OH-ZnTPP/mpg-C₃N₄ composite particles. The morphology, microstructure and composition of as-prepared nanocomposite particles are characterized by BET, SEM, XRD and XPS. The results show that the mpg-C₃N₄ is lamellar structure with porous, while the silver nanoparticles are dispersed on the surface or between the lamellar of the mpg-C₃N₄. The photoelectric property of the Ag/5-OH-ZnTPP/mpg-C₃N₄ nanocomposite particles is also characterized by UV-vis DRS, PL and PT, respectively. The results reveal that the visible-light utilization of mpg-C₃N₄ are improved by the introduction of silver nanoparticles and the sensitization of porphyrin. The catalytic activities are examined by using the reduction of 4-NP and the photocatalytic H2 production as model reactions, which demonstrates that the photocatalytic activity of mpg-C₃N₄ is enhanced after modified by silver nanoparticles and sensitized with dye porphyrins. Ag/5-OH-ZnTPP/mpg-C₃N₄ nanocomposite particles have high catalytic activity for the reduction of 4-NP and hydrogen production.