Silicon solar cell is well known as one of the cleanest and most potential renewable resources. As the major photovoltaic (PV) material in PV industry, multi-crystalline silicon (mc-Si) grown by directional solidification has recently attracted increasing attention because of its low production cost, low pollution and high throughput. Deeper understanding of the physic and optic properties, and preparation methods of the materials will lead to improved device design. This paper briefly presents basic directional solidification theory of multi-crystalline silicon, and reviews recent development of solar-grade multi-crystalline silicon. The directional solidification preparation techniques of high-quality solar-grade multi-crystalline silicon are detailed introduced and summarized. Furthermore, the existing problems and further development direction of directionally solidified multi-crystalline silicon for solar cell are discussed.