The Sn atom depth-profiles in the micro-phase region of the Ａｌ70Ｓｎ30 alloy surface for before and after the 27keV Ar+ ions bombardment have been studied using micro-beam Rutherford backscattering spectroscopy (M-RBS) analysis methods. The experimental results shown that the depth-profiles of the Sn atom between Al-rich phase region and Sn-rich phase region, and these phase regions locate on the unsputtered and sputtered surface are different.