Abstract: Micro porosity testing sample preparation process and matters needing attention for deformation aluminium and aluminium alloy ingot were introduced with 3104 aluminium alloy ingot as an example. And problems easily produced when rating the micro porosity grade according to the standard grade pictures were listed. Finally distribution rule of micro porosity in deformation aluminium and aluminium alloy ingot was studied through micro porosity testing at different positions and direction of 3104 aluminium alloy ingot.