The synthesis of polynuclear lanthanide-carboxylate complexes has received increasing interest due to their structural diversities and special properties such as porousity, optical, magnetic, electronic, etc.[1]. In continuation of our studies [2], here we report the results of the X-ray study of the lanthanum compound with cyanoacetate ligands of the composition {[La2(CNCH2COO)6(H2O)4]H2O}n, which is a linear polymer. Compound crystallizes in the triclinic centrosymmetric space groups P-1, a = 8.997(5)Å, b = 9.251(5) Å, c = 9.728(5) Å, α= 67.849(5)°, β= 84.224(5)° ,γ= 81.351(5)°. The inversion centers related asymmetric units is developed in 1D stricture through two types of bridges, Fig. 1. The La atom is bonded to La' by four of cyanoacetate ligands acting as syn–syn (c-2-c) bidentate bridges (La–O2, 2.455(2); La– O6, 2.490(2); La–O1', 2.511(2); La–O4', 2.450(2) Å), while with another symmetry related La'' through two tridentate (32-c) chelate-bridging ligands with the La – O3 and La – O3' bond lengths of 2.524(2) and 2.806(2) Å, respectively. The La ··· La' and La ··· La'' separation in the polymer chain are 4.755 and 4.608 Å, respectively. The shortening of the La ··· La'' distance compared with the La ··· La' one can be explained by different coordination modes of bridging ligands. The coordination number of lanthanum is completed to nine by the coordination of water molecules O(1w) and O(2w) (La–O(1w), 2.579(2) and La-O(2w), 2.664(2) Å). The coordination polyhedron of lanthanum is a monocapped tetragonal antiprism. In the crystal, polymer chains are united into a three-dimensional framework through a system of hydrogen bonds involving water molecules and nitrogen atoms of cyanoacetate ligands.