Newly prepared ZnBi12O20 can absorb light irradiation below 540 nm. The representative organic contaminant acetaldehyde is decomposed easily on this photocatalyst under visible-light irradiation (lambda > 440 nm). Wavelength dependence of CH3CHO decomposition proved further that the catalytic activity of this material is dominated by its light absorption. The theoretical calculations show that the VB of the photocatalyst is a hybridized band composed of O 2p, Zn 3d and Bi 6s. Furthermore, the band edge position of ZnBi12O20 was rough speculated according to the electronegativity of the constituent atoms. These calculation results confirm the strong oxidative property of the photocatalyst under the light illumination. (c) 2005 Elsevier B.V. All rights reserved.