A novel manganese(Ⅱ)-molybdenum(Ⅵ)-selenite(Ⅳ) oxide, namely, MnSeMoO6·H2O 1, has been hydrothermally synthesized with a high yield (82%).The structure of Mn(MoO3)(SeO3)(H2O) features a complicated 3D network composed of the 1D molybdenum(Ⅵ) oxide chains and the 1D manganese (Ⅱ) selenite chains interconnected via Se-O-Mo and Mn-O-Mo in which 1D 8-RMs channels exist along the a-axis.The results of magnetic property measurements indicate that there exist strong antiferromagnetic interactions between Mn(Ⅱ) centers.In addition, the visible-light-driven photocatalytic activity of the titled compound has also been investigated.The experimental result indicates that the sample shows good photoctalytic activity for degradation of azo dyes under visible light.