A three-dimensional conductive nanocomposite with an ordered conductive network and low percolation threshold has been successfully prepared by blending graphite nanosheets (GNs) with polyethylene on a two-roll mill. The conductive nanosheets orient intensively in the composite, leading to highly anisotropic properties. The nanocomposite with the fraction of conductive nanosheets closest to the percolation threshold possesses a sharp positive pressure coefficient of resistivity, in which the abrupt transition can be attributed to compressive-stress-induced deformation of the conductive network. Such piezoresistive effects depend strongly on filler morphology, filler spatial arrangement, and filler concentration.