Effects of boron and strontium combined treatment on the microstructure of hypoeutectic Al-7Si alloy have been studied. Experimental results show that strontium has no significant effect on the grain refinement efficiency of boron and the eutectic silicon modification efficiency is not only related to the strontium content but also related to the boron content in the Al-7Si alloy melt. There is a negative interaction between boron and strontium that results in the formation of a strontium-boron-aluminum containing compound, which reduces the effective strontium level and decreases the eutectic silicon modifciation efficiency substantially. The refinement and modification mechanisms remain unchanged after the combined addition of strontium and boron. Based on the experimental results, a model for assessing the modifciation level in the Al-Si alloy melts after combined addition of boron and strontium was presented. Effects of boron and strontium combined treatment on the microstructure of hypoeutectic Al-7Si alloy have been studied. Experimental results show that strontium has no significant effect on the grain refinement efficiency of boron and the eutectic silicon modification efficiency is not only related to the strontium content there is a negative interaction between boron and strontium that results in the formation of a strontium-boron-aluminum containing compound, which reduces the effective strontium level and decreases the eutectic silicon The refinement and modification mechanisms remain unchanged after the combined addition of strontium and boron. Based on the experimental results, a model for assessing the modifciation level in the Al-Si alloy melts after combined addition of boron and strontium was presented.