A crystalline silicon ingot and a method of fabricating the same are provided. The method utilizes a nucleation promotion layer to facilitate a plurality of silicon grains to nucleate on the nucleation promotion layer from a silicon melt and grow in a vertical direction into silicon grains until the silicon melt is completely solidified. The increment rate of defect density in the silicon ingot along the vertical direction has a range of 0.01%/mm˜10%/mm.