The effect of the pulse electric discharging (PED) on the solidification structure of pure aluminum during the directional solidification was investigated. Experimental results showed that fine microstructures were generated by exerting PED, and the cellular spacing decreased greatly with increasing current density. The effect of pulse electric discharge on the temperature gradient in front of the solid-liquid interface was analyzed, the cellular spacing was measured and expressed as the function of solidification processing parameter by using a nonlinear regression analysis, and the refinement mechanism using the PED treatment was also discussed.