We have developed a vacuum directional solidification device to prepare multi-crystalline silicon ingot using metallurgical-grade silicon. Microstructure and purity of the multi-crystalline silicon have been observed by OM （optical microscope） and inductive coupled plasma spectrumer. The results show that the microstructure of ingot exhibits coarse columnar crystal and the purity of multi-crystalline silicon can be increased from 99. 50% to 99. 86%

in which various impurities are reduced slightly.