A Bi-based oxychloride Bi3O4Cl with a layered structure as a novel efficient photocatalyst was studied in the present paper. The compound synthesized by a solid-state reaction method has a band gap of 2.79 eV. The material possesses a fair visible-light-induced photocatalytic activity. Generally, the photocatalytic efficiency of Bi3O4Cl for degrading methyl orange (MO) is higher than that of anatase TiO2 under UV light illumination. The dispersion of Ag over Bi3O4Cl leads to an obvious increase in the photocatalytic performance. The MO decolorization over Bi3O4Cl is mainly initiated by a photocatalytic process. The photocatalytic activity is discussed in close connection with the crystal structure and the electronic structure in details.