Abstarct: In this project, ZnO and ZnO-Ag nano-structures with the flower morphology as a photocatalyst were successfully prepared. ZnO with flower morphology was prepared via a simple solution route at the low-temperature. ZnO-Ag with different of Ag oloadings was prepared by photoreduction of Ag+ on the surface ZnO. The obtained ZnO-Ag and ZnO were characterized with TEM, XRD, SEM, EDX and AAS. The prepared photocatalysts were applied in photocatalytic degradation of methyl orange as model of organic pollutant under the UV irradition. The effects of various parameters such as pH, amounts of load Ag, UV exposed time during synthesis and etc were investigated. The results of the photocatalytic degradation of methyl orange (MO) in aqueous solution indicated that the ZnO-Ag photocatalyst exhibited better photocatalytic performance than ZnO. The enhancement of photocatalytic activity is due to the fact that the modification of ZnO with an appropriate amount of Ag can increase the separation efficiency of photogenerated electrons and holes.