This study reported the results of fabricating ZnO nanoparticles by an one-step sonochemical method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM). The photodegradation of Methylene Blue (MB) has been investigated in the presence of ZnO nanomaterials under Xenon light irradiation. The results showed that the degradation efficiency of MB (20 ppm, 200 mL) was about 93.1% after 75 minutes. The Intermediate product analysis and photocatalytic degradation pathway of MB were also studied.