A Ketjen Black-MnO composite was prepared by wet impregnation and TEM images showed that the MnO nanoparticles were well enwrapped by Ketjen Black (KB). The as-prepared KB-MnO composite were coated on one side of the commercial separators for the improvement of electrochemical performances of Lithium-Sulfur battery. For comparison, conventional separator coated by KB and conventional separator without coating was used in reference Lithium-Sulfur batteries. Electrochemical tests suggested that KB-MnO coated separator could act as the upper current collector and the barrier of lithium polisulfides which consequently achieved higher charge/discharge capacity and more stable cycling stability. Furthermore, TEM elemental map demonstrated that KB-MnO composite was more favorable for the adsorption of lithium polysulfides than KB, therefore the electrochemical performances of Li-S batteries can be dramatically enhanced.