The strengthening effects of Al-Zr-Cr-La dispersoids to Al-Mg alloys have investigated. The results show that adding Cr and La and adding Zr, Cr and La at tha same time can improve the hardness and strength and the capability to inhibit the recrystalization for the Al-Mg alloys. Comparing wih adding Cr and La, adding Zr, Cr and La at the same time has more obvious effect to inhibit the recrystalization and increase their hardness and strength