Graphene nanoribbons (GNRs) from longitudinal splitting of multiwalled carbon nanotubes are used as a conducting additive in LiFePO4 (LFPO) at the first time. Both SEM and TEM images show that LFPO particles are wrapped closely by GNRs with electrostatic interaction and embedded into a flexible network matrix of GNRs. Electrochemical experiments demonstrate that wrapping of GNRs is more effective to improve the electrochemical reaction activity of LFPO than mixing of carbon nanotubes. The comparative investigations on multiwalled carbon nanotubes and GNRs as a conducting additive in LFPO prove that longitudinal splitting of multiwalled carbon nanotubes will be a new way to prepare superior carbon conducting additives for high-rate lithium-ion batteries.