This letter reports a significant suppression on space charge in isotatic polypropylene (iPP) by inducing the growth of β-crystal doped with the nucleating agent N,N′-dicyclohexylterephthalamide (DCTH). The α- and β-crystals in iPP were analyzed, and their effect on space charge and distribution of trap level was studied. Results indicated that the doping of DCTH (0.1 wt. %) had great effect on the formation of the microcrystallite clusters of β-crystal, which makes the fraction of β microcrystallite (βc) markedly an increase from 0% to 83.2% in iPP. Compared to the dispersed microcrystallites of α-crystal, the growth of β-crystal effectively suppressed the space charge accumulation. It would attribute that the deep traps greatly weakened the mobility of charge carrier in iPP material.