Photocatalysts M3PW12O40 (M=NH4+, Cs+, Ag+, Cu2+) were prepared by microwave radiation solid-phase synthesis method. The results from SEM and XRD characterization reveal that the average particle size of M3PW12O40 is 15-80nm. Diffuse reflectance UV-vis spectra of M3PW12O40 shows that the absorption band shifted from 260 to 270-350nm and become broad in comparison with those of H3PW12O40. The results of photocatalytic degradation of formaldehyde prove that the shift of UV-vis absorption band is proportionally related to the activity of the catalyst. The Cu-3(PW12O40)(2) catalyst which has the maximal red shift to 350 nm of its UV-vis absorption band is found to be the most efficient catalyst. When the concentration of formaldehyde is 32.79 mg m(-3), the conversion of the formaldehyde is basically completed under the flow rate of 40 ml min(-1) over 0.19 M3PW12O40 catalyst. The M3PW12O40 catalysts prepared by this method are stable and the regeneration of the catalysts is easy. The catalysts have promising applications in the photocatalytic degradation of organic contamination. (c) 2006 Elsevier B.V. All rights reserved.