Abstract: The electrolytic low titanium Al-based alloy of Ti pre-alloying was used as raw material for producing the eutectic Al-Si ZL108Ti alloy.The refinement conditions of microstructure were studied.When Ti content was 0.10%~0.13wt%,effective refinement and high mechanical properties were obtained.The second dendrite arm spacing(DAS) of α-Al was 16.71μm.The average diameter of the eutectic Si particles was 2.69μm.Compared with the ZL108 alloy of no Ti addition,the ultimate tensile strength of ZL108Ti at room temperature and 300℃ increased 5% and 10% respectively.The mechanism of microstructure refinement might be described as follows.The sufficient component under-cooling was provided by the solute Ti which distributed uniformly among Al alloys melts.The sufficient component under-cooling activated more probable potential heteronuclei to nucleate the α-Al.Solute Ti could also strongly restrict growth of the grain.