In this investigation, cylindrical A356-5%50 μm SiCp and A356-10%100 μm SiCp castings of 40 mm diameter and 350 mm height were produced by stirring preparation and vertically upward suction casting process. The SiCp fractions in the casting different sections along the filling direction were quantitatively measured. The composite slurry flow during the casting mold filling was simulated based on the Euler method while the particle flow was calculated with the Lagrangian method for predicting the SiCp distribution. The simulated distributions were compared and validated with the experiment. It has shown that as the filling distance increased, the particle fractions decreased dramatically in the A356-10%100 μm SiCp casting while varied slightly in the A356-5%50 μm SiCp casting, and that the particles were prone to be aggregated near the mold wall at the filling beginning parts whereas more particles concentrated in the centre and fewer particles were present near the wall region in the casting front.