The construction of efficient conductive porous cathodes with prevention of polysulfides dissolution is essential for useful application of lithium-sulfur batteries. In this work, amicro-mesoporous carbon/magnesium oxide/sulfur composite is developed for lithium-sulfur batteries. The novel micro-mesoporous carbon powders grown on diatomite substrates by chemical vapor deposition provide efficient pathways for electron migration in the cathode and alleviate the structural failure caused by volume expansion. Our combined experimental and simulated results confirm that the synergistic magnesium oxides play an important role in anchoring lithium polysulfides. We find in this study that micro-mesoporous carbon/magnesium oxide/sulfur composite with 10 wt % magnesium oxide shows the best cycle and rate performance: a) the battery exhibits an initial specific capacity of 1143 mAh g(-1) at 0.2C and a reversible capacity of 592 mAh g(-1) after 500 cycles with an average of 99% columbic efficiency. b) A reversible discharge capacity of 664 mAh g(-1) is achieved after 400 cycles at 2 C which corresponds to a very small capacity decay per cycle similar to 0.065%. c) 90% reversible capacity remains after 200 cycles even under a current density as high as 5 C.