The composition distribution in Fe50Pd50 alloy ultrafine particles prepared by inert gas condensation method was investigated in details by means of X-ray diffraction technique through deconvolution of the X-ray diffraction data. The microscopic composition distribution in the alloy UFP was identified, which is caused by nonuniformity of the melt, fractional distillation during the evaporation process and statistical fluctuation during nucleation and coalescence of the alloy particles. The composition distribution affects the properties of the alloy UFP The composition distribution in Fe50Pd50 alloy ultrafine particles prepared by inert gas condensation method was investigated in details by means of X-ray diffraction technique through deconvolution of the X-ray diffraction data. The microscopic composition distribution in the alloy UFP was identified, which is caused by nonuniformity of the melt, fractional distillation during the evaporation process and statistical fluctuation during nucleation and coalescence of the alloy particles. The composition distribution affects the properties of the alloy UFP