Silicon solar cell has become the most important energy materials used in the photovoltaic (PV) industry field.In order to achieve wider practice application, decreasing fabrication costs, improving solar cell performances and reducing environment pollution are considered to be present primary development directions.In the present paper, a vacuum directional solidification with high temperature gradient is performed to prepare low cost solar-grade multicrystalline silicon (mc-Si) directly from metallurgical-grade mc-Si.The microstructure characteristic, grain size and boundary, solid/liquid growth interface, dislocation structure under different growth conditions are studied.The results show that directionally solidified multicrystalline silicon rods with high density and orientation can be successfully obtained when the solidification rate is below 60 μm/s.The grain size is gradually decreased with increasing the solidification rate.The control of obtaining planar solid-liquid interface at high temperature gradient is effective to produce well-aligned columnar grains along the solidification direction.The growth step and twin boundaries are preferred to form in the microstructure due to the faceted growth characteristic of mc-Si.The dislocation distribution is inhomogeneous within crystals and dislocation density increases with the increase of solidification rate.Furthermore, the crystal growth behavior and dislocation formation mechanism of mc-Si are discussed.