The title hydride and its deuteride were successfully synthesized. The heavy atom structure and hydrogen positions were determined respectively by X-ray Powder diffraction and time-of-flight neutron powder diffraction, They crystallize with a new monoclinic structure in space group I2 (No. 5); cell parameters: a = 12.575(1) Angstrom, b = 9.799(1) Angstrom, c = 7.9911(8) Angstrom, beta = 100,270(4)degrees (hydride), a = 12.552(1) Angstrom, b = 9.7826(8) Angstrom, c = 7.9816(7) Angstrom, beta = 100.286(4)degrees (deuteride), Z = 8. Sr2AlH7 is the first example that consists of isolated [AlH6] units and infinite one-dimensional twisted chains of edge-sharing [HSr4] tetrethedra along the crystallographic c axis.