Abstract: The crystal structure of the title compound was determined by single crystal X-raydiffractometny at - 90℃.It crystallizes in tetragonal space group P42₁c, with Z = 2,a =12.540(2), c = 17.565(5)Å.The structure was solved by direct and Fourier techniques andrefined by least-squares to R = 0.064 for 1737 reflections.Si ion is 4-coordinated, beingbonded to four oxygen atoms, Si-O = 1.595(11) Å Three M (Mo and V)are coordinated tosix Oatoms to form octahedron.M-O distances are in the range of 1.82～2.38Å and K atombeing coordinatred with seven O atoms, forms a monocapped trigonal prism.The K-O distances are in the range of 2.83～3.11Å.

Key words: erystal structure, K₄H(SiMo₁₁VO₄₀)·14H₂O