A green approach is developed for sol-gel synthesis of ZnO and ZnO2 through photochemical reaction under sunlight irradiation. The component and structure of the sol and powders are systematically analyzed, and the reaction equations are deduced and the fabrication mechanisms are discussed. It is found that the ZnO2 powder is obtained when sintering temperature is below 200 degrees C, while ZnO powder is obtained as sintering temperature increases from 200 to 800 degrees C. All ZnO and ZnO2 prepared by this method are with crystal structure and high purity. Our fabrication process has low energy consumption and it brings no environment pollution. This simple and green approach is considered of great potential applications in industry. (c) 2007 Elsevier B.V. All rights reserved.