The invention relates to a technology for separation of recrystallization and precipitated phase precipitation of low scandium Al-Mg alloy. In the technology, ingot castings are subjected to cold rolling at room temperature and the deformation is no less than 70%. then the alloy after cold rolling treatment is subjected to salt bath anneal for 1s-5min at the temperature interval of 340-525 DEG C, then is taken out and subjected to water quenching rapidly. Finally, the alloy after salt bath anneal is subjected to second anneal for 3h-36h at the temperature of 275-325 DEG C. The average crystal grain size of the alloy is less than 10 micrometers through the technology, and the average size of Al3(Sc, Zr) precipitation strengthening phase is below 10 nanometers.