It has been proved that the effect of amorphous polymer as the second component on the beta-nucleating effect of beta-nucleated isotactic polypropylene (iPP) blends was less than that of the crystalline polymers. We guess that it is the crystallinity of the second component that affects the beta-nucleating effect. In order to prove this hypothesis, the blends of beta-nucleated iPP and polyamide 6 (PA6) were prepared by melt compounding in this study. Cooling rate, crystallization temperature, crystallization time, annealing temperature and annealing time were used to control the crystallinity of PA6 phase, and the effect of PA6 crystallinity on the crystallization and melting behavior was studied, in turn its effect on the beta-nucleating effect of iPP phase was explored. The results indicated that beta crystal content markedly decreased with the increase of PA6 crystallinity, which proved that PA6 crystallinity controls the a-nucleating effect and suppresses the beta-nucleating effect of the beta-nucleating agent in the beta-nucleated iPP blends, leading to a significant decrease in beta crystal content. Therefore, decreasing the crystallinity of the second component in the beta-nucleated iPP blends is a feasible method to weaken alpha-nucleating effect of the second component and an effective way to obtain beta-nucleated iPP blend with high beta crystal content. (C) 2012 Elsevier B.V. All rights reserved.