The invention discloses a preparation method for casting columnar multi-crystal silicon with large crystal grains in the same crystal direction, which comprises the following steps: (1) sequentially putting single-crystal silicon blocks, silicon raw materials and doped elements in a crucible; (2) heating the crucible to melt the silicon raw materials and the doped elements on the single-crystal silicon blocks, wherein all single-crystal silicon block can not be completely melted; and (3) starting heat exchange from the bottom of the crucible, and using the single-crystal silicon blocks as seed crystals for induced growth and directional solidification to form the multi-crystal silicon. The columnar multi-crystal silicon with large crystal grains can effectively reduce the crystal boundarydensity in the materials and basically solves the problem of the reduction of the battery efficiency caused by the existence of a large number of crystal boundaries in the prior common process of casting the multi-crystal silicon; and meanwhile, the crystal grains in the multi-crystal silicon prepared by the invention have the same crystal direction, so that the high-efficiency alkaline wool making technology in the preparation process of batteries can be used, thereby improving the absorption efficiency of batteries for light.