It is an effective method to refine the solidification structure by applying pulsed current during the solidification process of metals. Many theories have been put forward to reveal the mechanism of grain refinement by the pulsed current. Taking pure aluminum as the studied material, under the condition that the process parameters such as the pulsed current parameters and pouring temperature were unchanged, two groups of experiments with different mold conditions were designed and conducted. It was found that the solidification structures of ingots changed with the mold conditions. Based on the mechanism of crystal rain, the formation process of solidification structure characteristics was discussed. Finally, it was pointed out that the melt flow had a great influence on the grain refinement by the pulsed current.