Solvent refining is a low-temperature and high refining efficiency Si purification process, in which Si recrystallization takes place from the supersaturated Si-based alloy melt depending on the retrograde behavior of impurity. More attentions have been focused on Si-Al alloy system, which is an economical alloy and can effectively lower the content of B and P. However, the B segregation mechanisms during the alloy solidification process is lack, and the refined silicon can not be separated effectively from the alloy, resulting in a waste of energy and time. In this work, Al and Sn were used as solvent metals to purify metallurgical grade silicon and the segregation behaviours of B were initially clarified. Moreover, the effect of direct electric current on redistribution and microstructure of primary silicon in alloy simple has been studied. This method was attempted by the directional solidification method in order to separate Si from the alloy.