A nanometer coupled oxide ZnO-SnO2 was prepared using the co-precipitation method employing NH3-H2O as the precipitant. The oxide was characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and UV diffuse reflectance spectrum (DRS). The photocatalytic activity of nanometer coupled oxides was studied using methyl orange as a mode organic pollutant. The relationship between the photocatalytic activity and the microstructure of nanometer coupled oxides was also discussed in the paper. Experimental results showed that the nanometer coupled oxides mainly consist of nanometer ZnO and SnO2, and they have the same excellent photocatalytic activity as Degussa P25 TiO2 for the degradation of methyl orange (MO). Moreover, the photocatalytic activity of the coupled oxides increases gently at first, then decreases rapidly with the increase of the calcination temperature. But a small amount of nanometer Zn2SnO4 was formed in the mixture of coupled oxides when the calcination temperature was higher than 700degreesC. (C) 2003 Elsevier B.V. All rights reserved.