In this research work, ProCAST software is employed to study the sand casting process of a box-type part for wind turbine. The casting part is big in size, non-uniform in wall thickness, and heavy in some local positions. Shrinkage cavity and porosity are very likely to from at these locations. By numerical simulation, the influence of the parameters such as pouring temperature, chills, riser on mold filling and solidification is analyzed. Simulation researches reveal that with appropriate pouring temperature, correct number, size and location of chills and risers, a smooth mold filling, reduced shrinkage and other defects are available and desired sound castings can be produced.