An unprecedented extended architecture, Na₈H₂L(H₂enMe)₄{Mn(H₂O)₂[(W₄Mn₄O₁₂)(P₂W₁₄O₅₄)₂]}·17H₂O, (1, Na₈H₂L(H₂enMe)₄[1a]·17H₂O, enMe = 1,2-diaminopropane) constructed from double-Dawson type polyoxoanions (DDTP) has been successfully synthesized under hydrothermal conditions. Single-crystal X-ray diffraction analysis is carried out on 1, which crystallizes in the monoclinic system, space groupC2/c, a = 43.974(9) Å, b = 13.869(3) Å, c = 28.385(6) Å, β = 71.34(3)°, V = 15308(5) ų, and Z = 4. Polyoxoanion 1a exhibits a double-Dawson-type structure which is composed of two tetra-substituted-Dawson anions. These DDTPs are further connected by Mn²⁺ linkers into the one-dimensional (1D) inorganic chains. To the best of our knowledge, it is the first example of an inorganic chain constructed from DDTPs. The 1D inorganic chains are further connected into a 3D supramolecular structure viahydrogen bonding interactions between 1,2-enMe molecules, H₂L ligands and the DDTP. Electrocatalytic studies indicate that compound 1 displays electrocatalytic activity toward the reduction of nitrite.