Primary Si particle size has been refined as Ca content of the melts decreased and cooling rate increased. A control of Ca content by the addition Of CuCl2 to the melt was the most efficient in the refinement of primary Si particles. The minimum size of primary Si particles in this study was 15.0mum when a residual content of Ca element in the alloy was 5ppm. Primary Si particle size was refined as primary Si crystallization temperature increased, which was attributed to the decrease of Ca content in the melts.