Complex formation of iron(III) with 1-phenyl-2,3-dimetylpirazolon-5-azopyrogallol has researched by the spectrofotometric method and has studied effect of 8-oxyquinoline to the complex formation. It has determined the formation of Fe(III)–R–Ox mixedligand complex with 1:1:1 ratio in presence of 8-oxyquinoline. By formation of this complex it observes bathchromic shift and hyperchromic effect in the absorption spectrum and the maximum yield shifts to acid condition. It has established the optimal formation condition, it has determined the compositions and stability constants and main spectrometric characteristics of binary and mixedligand complexes of iron(III) has calculated. It has offered the new methodic of photometric determination of iron(III) in the form of a Fe(III)–R–Ox mixedligand complex, which is applicable for the determination of its in an aluminum alloy A386-1