Abstract: The microstructure and properties of a new Al-Zn-Mg-Cu-Zr-Sc alloy profile after extruding and two-step aging were studied using optical microscopy (OM), scanning electron microscopy (SEM), electronic back-scattered diffraction technique (EBSD), transmission electron microscopy (TEM) and tensile test. The results show that after two-step aging treatment, the tensile strength, yield strength, elongation and electrical conductivity of the alloy were 540 MPa, 507 MPa, 11.1% and 41.7 %IACS, respectively. With the minor addition of Sc, the tensile strength and yield strength increased by 4.5% and 4.7%, and the elongation and electrical conductivity almost didn′t change. Scandium existed as Al3(Sc,Zr) phase which can refine grain size of the alloy, effectively restrain the recrystallization behavior and the appearance of precipitate free zones along grain boundaries and coarsing of precipitates on the grain boundaries. In addition, a ternary W phase composed of elements Al, Cu and Sc was observed in the alloy.