A deformable permanent magnetic alloy, with composition of 62Pe-23Cr-15Co (in wt %), has been studied by high-temperature X-ray diffraction method. Debye-Scher-rer photographs of samples treated with aging in magnetic field and also of those treated without magnetic field were taken. It has been observed that the transformation process with rising temperature up to 800℃ is different in the two classes of samples. The lattice parameters of the samples without a treatment in magnetic field have been measured at various temperatures; and it has been found that in these samples a transitional phase unknown before appeared at 610℃, which was unstable at other temperatures.