A new Fe3C-N-doped reduced graphene oxide (Fe3C-N-rGO) prepared by a facile method is used as a separator for high performance lithium-sulfur (Li-S) batteries. The Fe3C-N-rGO is coated on the surface of commercial polypropylene separator (Celgard 2400) close to the sulfur cathode. The special nanotubes are in-situ catalyzed by Fe3C nanoparticles. They could entrap lithium polysulfides (LiPSs) to restrain the shuttle effect and reduce the loss of active material. The battery with the modified separator and sulfur cathode shows an excellent cycle performance. It has a high rate performance, 580.5 mAh/g at the high current rate of 4 C relative to 1075 mAh/g at 0.1 C. It also has an initial discharge capacity of 774.8 mAh/g measured at 0.5 C and remains 721.8 mAh/g after 100 cycles with a high capacity retention of 93.2%. The outstanding performances are notable in recently reports with modified separator.