A new bi-capped Keggin heteropoly molybdovanadated derivative, [Co (en)3]2[SiMo8V6O42]∙6H2O (1) (en = ethylendiamine) has been hydrothermally synthesized and structurally characterized by the elemental analysis, IR, XPS and single crystal X-ray diffraction. The crystal structure analysis reveals that compound 1 consists of [Co (en)3]2+transition metal coordination fragment and the [SiMo8V6O42]4-building blocks, which are linked together via hydrogen-bonding interactions to form a new 3-D supramolecular networks.