Abstract: The microstructural features of pure iron after surface mechanical attrition treatment(SMAT),such as effective grain (subgrain) size,micro-distortion,dislocation density and elastic stored energy density,were determined by the X-ray line profile analysis(XLPA).The microstructure was observed by SEM and compared to tensile samples with 40% deformation.The results indicate that for pure iron sample prepared by SMAT for 90 min the average dislocation density was 1.0×1016 m-2 and the effective grain size was about 7 nm,which produced the most effective grain refinement and the greatest micro-distortion compared with the tensile sample.The grain sizes determined by XLPA and TEM methods were very close.