Abstract: Based on the behavior of pressure and flow velocity during semisolid A1Si7Mg slurry filling processes, a three dimensional model of slurry flow coupled with apparent viscosity is established. Relating to boundary condition and cavity air pressure, simulation on semisolid aluminum alloy casting has been investigated with the help of the SOLA-VOF algorithm. It is shown that flow velocity of semisolid slurry have mark effects on the flow patterns. Lower flow velocity result in mold filling steadily and prevent gas porosity. Under certain flow velocity, using process in which mold filling along the radial lead to lower filling resistance when compared with the axial, none of these castings have defects. Finally, simulation results is in agreement with the experimental results.