Space charge injection and accumulation is attracting much attention in the field of dielectric insulation especially for electronic devices, power equipment and so on. This paper proposes using the inhibition effect of graphene for the injection and accumulation of space charge in low-density polyethylene (LDPE). Scanning electron microscope (SEM) and transmission electron microscopy (TEM) images were employed to observe the dispersion of graphene with a two-dimensional structure in LDPE. The time-dependent space charge dynamic behaviors of graphene/LDPE nanocomposites with the filler content of 0, 0.003, 0.005, 0.007 and 0.01 wt % were characterized by the pulsed electro-acoustic (PEA) test at 40, 60 and 80 °C, and the charge mobility was evaluated by its depolarization processes. The experimental results show that for the undoped LDPE film, large amounts of space charges were injected from the electrodes into samples, especially at 60 and 80 °C. The graphene/LDPE nanocomposites with a filler content of 0.005 wt % could markedly suppress the space charge injection and accumulation even at 80 °C, which is attributed to the large quantities of graphene-polymer in interface regions. These interface regions introduced numbers of deep trap sites within the forbidden band of nanocomposites, which can reduce the de-trapping rate of charges and suppress the space charge accumulation in the polymer bulks. The graphene/LDPE nanocomposites are suggested for dielectric applications, intending the inhibition of space charge injection and accumulation.