The effect of Sc on microstructure an d tensile p roperties of Al-Li-Cu-Mg-Ag-Zr alloy has been studied using o ptical and t ransmission electron microscopy and scanning electron microscopy.The results sh ow that addition of Sc may refine the gra in size,and encourages the homogeneou s precipitation of T 1 phase throughout the matrix,The wid espread precipitation of T 1 phase promotes homogeneous deforma tion thereby improving the mechanical pr operties of these trace-Sc containi ng.