To reduce the energy consumption and avoid the secondary contaminants caused by the use of additives during unsymmetrical dimethylhydrazine (UDMH) wastewater treatment, a kind of TiO₂ nanorod array (NRAs)/CdS/Au thin film photocatalyst with visible light response was prepared. Results show that TiO₂ NRAs/CdS/Au composite film can degrade UDMH using visible light, and when using the simulated sun light as light source. the degrading effect of composite film on UDMH was better that of composite film on UDMH when using the pure visible light as light source. The degradation rate of UDMH decreases gradually along with the increase of initial concentration of UDMH, but the total degradation concentration increases. The suitable pH for the photocatalytic degradation of UDMH wastewater by TiO₂ NRAs/CdS/Au composite film is about 7.2. Addition of hole-capture scavenger, hydroxyl radical scavenger and pumping nitrogen gas all make the degradation rate of UDMH decrease, while pumping air makes the degradation rate of UDMH increase. The TiO₂ NRAs/CdS/Au composite film can degrade the toxic substances, nitrosyldimethylamine (NDMA) and formaldehyde dimethylhydrazone (FDMH), which are produced during the degradation of UDMH when the irradiation of simulated sunlight and visible light respectively, but the degradation effect of the simulated sunlight is better and pumping ozone can help the rapid removal of NDMA and FDMH.