Variations of cooling characteristics and solidification microstructure were investigated at various melt pouring temperature, mold temperature and cooling condition for semi-solid slurry of A356 alloy. And metallurgical and mechanical properties were examined with testing samples made by rheocast process based on the obtained cooling conditions. Undercooled state of melt appeared when superheating of melt was below 35, and it was easy to form equiaxed solidification structure. Forced cooling hardly ever contributed to globular shaping of microstructure although it helped a little to refine microstructure. And slow cooling through insulation and mold heating was effective to form globular shape. Also, the metallurgical and mechanical properties of samples made by this process were better than those of other sample made by conventional processes.