Strong magnetic field method was adopted to solve the problems,such as the loss of efficiency after re-melt,the short effective time after Na modification,and the primary Si distributed unevenly after P modification.Al-6%Si hypoeutectic alloy and Al-12.6%Si eutectic alloy were modified with Na-salt,and Al-18%Si hypereutectic alloy was modified with P-salt in strong magnetic field respectively.The experimental results show that for Al6%Si hypoeutectic alloy,the magnetic field can avoid the loss of efficiency,and for Al-12.6%Si eutectic alloy,the strong magnetic field can prolong the effective time of the modification.For Al-18%Si hypereutectic alloy,the primary Si distributes evenly when the strong magnetic field imposed.Experimental results also show that the strong magnetic field can improve the modification.