Abstract: With the increasing demand for cable, environmental protection and energy-saving insulation has become a new development trend, and the research and development of polypropylene (PP) has become the first choice of dielectric researchers. In order to improve dielectric properties of polypropylene-elastomer blends, MMT-POE/PP nano-modified blends were prepared by two-step melting blending method with two different compatibilizers and organically treated montmorillonite (MMT). And then the effects of interphase dispersion states of nanoparticles in different phase zones on dielectric properties of nano-modified blends were investigated. The microstructure, crystalline morphology and crystallization parameters were characterized by SEM, electrostatic force microscopy (EFM), polarizing microscope (PLM) and DSC. The micro-mechanism of phase dispersion on MMT-POE/PP composites was discussed through the breakdown properties test of the blend sample. The experimental results show that when MMT layers tend to disperse in the PP phase, the crystallization size decreases about 5.9 μm, the crystallization speed increases, and the crystallinity increases about 2.1%. And then the dielectric constant and insulation conductivity decrease obviously, and the alternating current (AC) breakdown field strength increases from 82.69 kV/mm to 95.16 kV/mm. The dielectric properties of nano-modified blends can be positively improved by regulating the tendency of nanoparticles to disperse uniformly in the PP phase.