A new kind of three-component nanomaterials-In2S3-Ag/TiO2 nanotube arrays was first synthesized in two-step deposition method. In this study, the morphology, elements, crystal structure and photoelectric property testing of the three-component photocatalyst were characterized by scanning electron microscope (SEM) and fluorescence photoluminescence spectra (PL), etc. The three-component photocatalyst was applied to the photodegradation 2,4-dichlorophenoxyacetic acetic acid (2,4-D). The photocatalytic degradation experiment results of 2,4-D have shown that its 100% removal rate can be achieved within 140 minutes. The unique two-step excitation process in the three-component In2S3-Ag/TiO2NTs system leads to the significant improvement of photocatalytic ability. The experiments indicate that different values of pH and the concentration of 2,4-D have significant effect on degradation. The preliminary results show that the photocatalytic reactions are optimized at pH 4.23, higher or lower pH levels will reduce the removal rate due to the phase change of 2,4-D molecules. The photocatalytic degradation mechanism was also analyzed with equations and model diagrams.