Carbon host materials play an important role in improving the electrochemical performances of lithium-sulfur batteries. In this work, we have successfully prepared nitrogen-doped porous carbon nanosheets (NPCN) by using low-cost raw materials (monosodium glutamate) via a facile carbonization approach without any activation process. The obtained NPCN-800 possesses a special micro/mesoporous structure, with a relatively high BET surface area and appropriate nitrogen doping. By employing the NPCN-800 as a reservoir to impregnate sulfur as the cathode material of lithium-sulfur batteries, the resulting sulfur/carbon composite with 65.5 wt% sulfur exhibits an initial discharge capacity of 1070 mAh g(-1) at 0.2 C and enhanced capacity retention of 680 mAh g(-1) after 150 cycles. Moreover, a capacity of 452 mAh g(-1) at 0.5 C is achieved over 200 cycles with 98.6% Coulombic efficiency. The superior electrochemical performance is attributed to the synergistic effect of the hierarchical porous structure (physisorption) and N-doping (chemisorption).