A facile and scalable route for the in-situ synthesis of porous MnO/C nanocomposite by annealing Mn3(C6H5O7)2 precursor has been developed. MnO particles were encapsulated inside the carbon matrix to form a skeletal architecture. Such a mesoporous structure provided more active sites and effective channels for Li+ and electrolyte, and act as the supporting structure for MnO particles during the cycling process. As an anode material for lithium ion batteries, the porous MnO/C composite had a specific capacity of 831.7 mAh g−1 at 100 mA g−1 and delivered a stable cycling capacity of 564.1 mAh g−1 after 59 cycles, indicating that the porous MnO/C nanocomposite could significantly improve the structural stability and might be a suitable electrode material for lithium-ion batteries.