Er and Sr were added to 5052 Al alloy to investigate their possible effects on the microstructure and mechanical properties of the alloy. The results show that while Sr addition has a moderate grain refinement effect and has no positive effect on alloy plasticity, Er addition refines both the grain size and Al6Fe intermetallics and obviously improves the tensile elongation from 12% for 5052 alloy to 20% for Er-containing alloy. It is also revealed that Er either dissolves in the matrix or combines with Fe and Si and that Er can purify the alloy by eliminating impurity elements Fe and Si from the melt and Al-matrix.