Abstract: To prepare nano-size ZnO, the zinc acetate and lithium hydroxide was used as raw material and ethanol as the solvent. The sol-gel method supplemented with microwave radiation was adopted. The samples were characterized by powder X-ray diffraction, UV-Vis spectroscopy, energy dispersive X-ray spectrum and electron microscopy. Under the condition of different microwave radiating times, the photocatalytic performance of prepared ZnO samples was studied using UV light as illumination device and XB-R as stimulant pollutant. The characterization and catalytic activities of ZnO prepared with microwave method are compared with that of one prepared using traditional sol-gel method. The results indicate that microwave synthesized ZnO has a smaller particle size and better photocatalytic activity than traditionally prepared ZnO. Sample with 30 minutes microwave radiation has the best performance. Its degradation ratio could reach 90 percent when 100 mL XB-R with the density 20 mg/L and 10 mg nano-size ZnO is irradiated under UV light for 40 minutes.