The chemical procedure for preparing Al 2O 3 sample used in AMS was reported. The fact that different ions are precipitated at different pH values was used to purify Al which was coverted to Al 2O 3 at high tempareture. A set of Al 2O 3 samples including standard and blank have been prepared. For the blank the ratio 26 Al/ 27 Al was measured to be 1.1×10 -13 . The result showed that the interference of 26 Mg in sample was negligible and the chemical procedure of preparing Al 2O 3 samples were successful. The measurement procedure of 26 Al by AMS was also reported.