Abstract: In order to prepare high dielectric constant composites, pristine multi-walled carbon nanotubes (P-MWCNTs)/poly(vinylidene fluoride) (PVDF) composites and graphitized multi-walled carbon nanotubes (G-MWCNTs)/PVDF composites were prepared by injection molded method. Then G-MWCNTs and P-MWCNTs were characterized by Raman spectroscopy, and the fracture morphologies, mechanical properites and electrical properties of MWCNTs/PVDF composites were measured. The results show that G-MWCNTs have higher purity and crystallinity than those of P-MWCNTs. Two kinds of different MWCNTs both disperse in the PVDF matrix uniformly. The addition of MWCNTs affects the mechanical behaviors of PVDF significantly. The dielectric properties of MWCNTs/PVDF composites enhance with the content of MWCNTs increasing. Compared with P-MWCNTs, G-MWCNTs reduce the percolation threshold of the composites effectively. When the frequency is 100 Hz, the dielectric constant of pure PVDF is 7.0; when the content of P-MWCNTs is 5wt%, the dielectric constant of composites is 23.8; when the content of G-MWCNTs is 5wt%, the dielectric constant of composites reachs up to 105.0. The MWCNTs/PVDF composites prepared by injection molded method remain relatively low conductivity, thus resulting in a lower energy loss and having great significances for the charge storage applications.