A new type of nano-sized cobalt oxide compounded with mesoporous carbon spheres (MCS) as negative electrode material for lithium-ion batteries was synthesized. The composite containing about 20wt.% cobalt oxide exhibits a reversible capacity of 703mAh/g at a constant current density of 70mA/g between 0.01 and 3.0V (vs. Li+/Li), and remains a capacity retention of 77% after the 30th cycle. The improvement could be attributed to that the MCS had a good electronic conductivity and severed as dispersing medium to prevent cobalt oxide nanoparticles from aggregating, and the mesopores (cobalt oxide not fully occupied) can provide the enough space to buffer the volume change during the Li-ion insertion and extraction reactions in cobalt oxide nanoparticles.