Abstract: Taking Al-7Mg-Zr alloy as matrix, Al-7Mg-0.2Zr-0.3Er, Al-7Mg-0.2Zr-0.3Sc and Al-7Mg-0.2Zr-0.15 alloys were fabricated by semi-continuous chill casting ingot with the co-addition of trace Sc and Er. The effects of trace Sc, Zr addition on the microstructure and mechanical properties of these alloys were investigated. The results show that the addition of Sc or co-addition Sc/Er are both able to decrease the average grain size of ingots, by contrast, the grain refinement effect of addition Er is not obvious. After 350 ℃/12 h homogenization treatment, many uniformly distributed nano-scale Al3（Sc, Zr）/Al3（Er, Zr） precipitate in Al-7Mg-0.2Zr-0.3Sc and Al-7Mg-0.2Zr-0.15Sc-0.3Er alloy matrix, which can create remarkable strengthening and the ultimate tensile strength of the above alloys increases to 324 MPa and 301 MPa, respectively.However, the Al3（Er, Zr） precipitating in Al-7Mg-0.2Zr-0.3Er alloy have large size and relatively weak strengthening effect,therefore, the tensile strength of the alloy is only 236 MPa.