Au modified ZnO nanoparticales (Au/ZnO) were successfully prepared by a simple sonochemical method, without adding any active agent. The as-prepared products were characterized by SEM, TEM, XRD, PL, UV-VIS, UV-DRS and BET. The results show that Au3+ is directly reduced on the surface of ZnO to form nanoparticles by sonochemical method, and Au nanoparticles preferentially grow along the surface of ZnO, thus forming a close interface structure between the two materials. The modification of Au nanoparticles makes the UV peak at 384 nm shifts to blue and its intensity is obviously weakened, meanwhile, the intensity of visible luminescence peak decreases until it disappears, indicating that the photo-generated charges are effectively separated. With an appropriate amount of gold decoration, the UV light absorption capacity of the Au/ZnO was significantly enhanced, and a certain degree of visible light absorption appeared, indicating that the light utilization rate has been improved. Photocatalytic experiments show that Au/ZnO can effectively degrade methyl orange and methyl blue solutions. Kinetic analysis of the photodegradation properties using ln(ρ/ρt)=kt linear fitting shows that as the amount of Au is 0.5% (based on the amount of ZnO substance, the same below), the first order degradation reaction rate constant of methylene blue and methyl orange is 4.26 and 2.38 times of pure ZnO, respectively, and their degradation can reach 100%.