In this study, two kinds of Al–La master alloys were prepared by ultrasonic method and ordinary mixmelting method, and both of the alloys were added into the Al alloy.Then, the microstructure of Al–La master alloy and the modification effect on the Al alloy were investigated using optical microscope(OM), X-ray diffraction(XRD), scanning electron microscope(SEM), and energy disperse spectroscopy(EDS).The results show that because of ultrasonic cavitation and streaming, the grain size of Al–La master alloy prepared by the ultrasonic method is refined, which distributes evenly.And, there is no gas hole,inclusion, or segregation in the Al–La master alloy with aAl, La, and La3Al11.Furthermore, Al–La master alloys show a nice modification for Al alloy, which is much better than that prepared by ordinary mix-melting method. In this study, two kinds of Al-La master alloys were prepared by ultrasonic method and ordinary mixmelting method, and both of the alloys were added into the Al alloy.Then, the microstructure of Al-La master alloy and the modification effect on the Al alloys were investigated using optical microscope (OM), X-ray diffraction (XRD), scanning electron microscope (SEM), and energy disperse spectroscopy (EDS). The results show that because of ultrasonic cavitation and streaming, the grain size of Al -La master alloy prepared by the ultrasonic method is refined, which distributes evenly. And there is no gas hole, inclusion, or segregation in the Al-La master alloy with aAl, La, and La3Al11.Furthermore, Al-La master alloys show a nice modification for Al alloy, which is much better than that prepared by ordinary mix-melting method.