This article investigates the effect of Ti on the microstructure of hypereutectic aluminum silicon alloy (Si: 15wt.%). The hypereutectic aluminum silicon alloy (Si: 15wt.%) was modified by Al-10% Ti intermediate alloy. The research results indicate that Ti has a significant refining effect on primary silicon and eutectic silicon in aluminum silicon alloy (Si: 15wt.%). With the increase of Ti addition, the grain size of primary silicon in the alloy shows a trend of first decreasing and then increasing. When the amount of Ti added is 0.7%, the grain size of primary silicon has been refined from unmodified 30–40 μm to 10–20 μm and its sharp edges have been passivated. The eutectic silicon structure has changed from long needle like to point like and thin short rod like. The XRD analysis results indicate that no intermediate phase was detected in the aluminum silicon alloy (Si: 15wt.%) after modification. The SEM analysis results indicate that coarse needle like structures are formed in the aluminum silicon alloy (Si: 15wt.%) after modification, which is an Al-Si-Ti ternary compound.