A com. Fe catalyst for NH(3) synthesis was modified by addn. of CaO, Al(2)O(3) and K(2)O promotors, reduced with H(2) and then oxidized with O(2) at 500-500 degrees C, O(2) + N(2) mixt. at 100 degrees C, CO(2) + N(2) at 300-500 degrees C or H(2)O + N(2) at 300-500 degrees C. The oxidized catalyst samples were studied by thermogravimetry, X-ray diffraction anal., t.-programmed redn., Mossbauer spectroscopy, transmission electron microscopy, plasma-induced at. emission spectroscopy, thermal desorption and manganometric anal. The highest stability of the catalyst was achieved when it was oxidized preliminary with a mixt. of N(2) with H(2)O or CO(2) and finally oxidized with O(2). The stable surface layer of the catalyst contained Fe(8)AlO(12) spinel.