In order to investigate the change in liquid microstructure of Al-Si alloy treated by electric pulse (EP), X-ray diffraction tests with liquid Al-Si alloy and ZL109 alloy treated or not by EP were carried out. The results show that the number of Al-Si atomic clusters decreases and that of A1-A1 and Si-Si atomic clusters increases for the treated samples. The tests with ZL109 alloy indicate that a large amount of primary crystal Si appears in the solidified microstructure after treated by EP. It is found that EP can change the microstructure of liquid metal by affecting the probability of electrons appearing in different atoms (Al and Si) in the liquid metal. The combining force of different atoms decreases relatively, and that of the same atoms increases, which is the main reason of reducing the atomic cluster with different atoms (Al-Si) and increasing the atomic cluster with the same atoms (Al-Al, Si-Si). The increasing of the atomic cluster with the same atom cluster resulted in the increasing of Si In order to investigate the change in liquid microstructure of Al-Si alloy treated by electric pulse (EP), X-ray diffraction tests with liquid Al-Si alloy and ZL109 alloy treated or not by EP were carried out. The results show that the number of Al-Si atomic clusters decreases and that of A1-A1 and Si-Si atomic clusters increases for the treated samples. The tests with ZL109 alloy indicate that a large amount of primary crystal Si appears in the solidified microstructure after treated by EP. It is found that EP can change the microstructure of liquid metal by affecting the probability of electrons appearing in different atoms (Al and Si) in the liquid metal. The combining force of different atoms decreases relatively, and that of the same atoms increases, which is the main reason of reducing the atomic cluster with different atoms (Al-Si) and increasing the atomic cluster with the same atoms (Al-Al, Si-Si). The increasing of the atomic cluster with the same atom cluster resulted in the increasing of Si