Abstract: Effects of ultrasonic and peritectics on the Microstructure of Al alloys were investigated by the addition of four peritectic-forming solutes (Ti,Nb,Zr,V) on the aluminum melt. The microstructure of Al alloys with ultrasonic vibration treatment and without ultrasonic vibration for comparison when different growth restriction factor, i.e. Q, was studied by optical microscopy, scanning electron microscopy, energy dispersive spectrometer analysis and XRD. The results show that ultrasonic vibration obviously improves the microstructure and with the increase of solute,Q value is bigger, grain size is smaller, a linear relationship with grain size and 1/Q. When the solute reach a certain,Q value remains unchanged, the effect of grain refinement is better. It is found that peritectic-for-ming solutes do not only cause grain refinement by their segregation power, i.e. the constitutional undercooling contribution but, more importantly, introduce Al₃Ti、Al₃Nb、Al₃Zr、Al₃Zr₄、Al₂₁V₂、Al₃V etc. potent nucleant particles into the melt via heterogeneous nucleation can promote grain refinement significantly.