The properties of aluminum alloys are developing towards high specific strength, high specific modulus, high damage tolerance, heat resistance and corrosion resistance. Microalloying is an important means to improve the properties of aluminum alloys. A large number of studies have shown that adding cheap element Er to aluminum alloys can play an effective role in microalloying. In this paper, the structure and precipitation of Al-Er phase are summarized, and the role of Er in several types of industrial aluminum alloys, cast aluminum alloys and 3D printed aluminum alloys is reviewed. Microalloying element Er can form nano sized Al3Er strengthening phase in aluminum alloys, under the same atomic content, the dispersion precipitation strengthening effect of Al3Er is more significant than that of Al3Sc. The addition of Er element and the precipitation of Al3Er phase can obviously refine the aluminum alloys structure, increase the recrystallization temperature, promote the precipitation of main strengthening phases, and greatly improve the strength or plasticity of aluminum alloys. Er can also form high stability Al3(ErZr) and other composite strengthening phases with Zr and other elements, through its multilevel action mechanism on dislocation substructure and grain morphology regulation, Er can effectively improve the comprehensive properties of aluminum alloys, such as heat resistance, corrosion resistance and 3D printing crack suppression. At present, the microalloying element Er and its composite microalloying have been successfully applied in Al-Cu system, Al-Mg system, Al-Zn-Mg system, some cast aluminum alloys and 3D printed aluminum alloys, and become an important method to improve the comprehensive properties of aluminum alloys.