The conductive polymer composite (CPC) based on carbon black (CB), polyethylene (PE), and poly(ethylene terephthalate) (PET) was fabricated, in which the majority of CB particles were selectively localized in the surface of in situ deformed, highly oriented PET microfibrils. The on-line measurement of the electrical resistivity of the CPC materials indicated that the critical time for conductive network formation decreased with the increase of the annealing temperature and the filler loading. The activation energy for conductive network formation was about 96 kJ/mol, which was much higher than that for common CB/PE composite due to the large size of the conductive microfibrils. By a thermodynamic percolation model, the percolation threshold at equilibrium state was 1.735 vol.%, below which the effective conductive network was never formed. The reorganization velocity of the conductive microfibrils was a function of annealing temperature. This study extended insight into the dynamic process of the conductive network formation during annealing.