To study the interaction between -nucleation agent and nano-CaCO3 in iPP matrix, the dynamic rheology properties, crystallization and melting behaviors, impact fracture surface of -nucleation agent (-NA) nucleated and nano-CaCO3 filled iPP were investigated in details in this study. Under suitable conditions, the -NA has a promoting dispersion effect on the dispersion of nano-CaCO3 in PP matrix. However, 0.2 wt % -NA nucleated sample has a worse promoting dispersion effect than 0.05 wt % -NA nucleated sample at relatively high nano-CaCO3 content (7.5 wt %). The reason is that 0.2 wt % -NA aggregates on the surface of nano-CaCO3 agglomerations. The crystals induced from -crystals grow more regular and perfect than conventional crystals. For the relative fraction of crystals (K), the nano-CaCO3 content has little influence on 0.05 wt % -NA nucleated samples, but obvious effect on 0.2 wt % -NA nucleated samples. Based on the investigated results, a mechanism model about the interaction between -nucleation agent and nano-CaCO3 in iPP matrix is proposed. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013