Polycrystalline Sm0.55Sr0.45MnO3 was prepared by solid-state reaction at 1300 °C. Single phase of the compound was analysed by a powder X-ray diffraction technique. The powder pattern of Sm1−xSrxMnO3 was indexed and refined using a General Structure Analysis System (GSAS) to an orthorhombic structure with space group Pnma, a = 5.4323(7), b = 7.6585(4), and c = 5.4343(7) Å.