Abstract: Using electron microscopy and X-ray diffraction techniques, the structure changes of Fe-Cr-Al alloy being used at low temperature for a long time were investigated. The results demonstrated that increase in embri-ttlement for the alloy was mainly caused by grain growth and α'-phase precipitation which contained 75 at% Cr; as usual, Small amount σ-phase and carbide Gr₂₃C₆ precipitated at grain boundaries.