Nanospherical-like manganese monoxide/reduced graphene oxide (MnO/rGO) nanocomposites are synthesized by using an electron beam radiation approach in an aqueous solution containing potassium permanganate and graphene oxide in the presence of acetone as radical scavenger and subsequently calcining in flowing Ar atmosphere. SEM and TEM observations show that nanospherical-like MnO with average size of 20nm are firmly anchored onto the rGO to form MnO/rGO nanocomposites. The typical MnO/rGO nanocomposite exhibits a high initial reversible capacity (977.1mAhg−1) at a current density of 150mAg−1 and delivers 648.4mAhg−1 at a rate of 750mAhg−1 with excellent cycling performance (89% of capacity retention over 50 cycles), which indicates that the MnO/rGO nanocomposite is a promising anode candidate for Li-ion batteries. Furthermore, the facile synthetic strategy by using an electron beam radiation provides a novel avenue for making high-performance metal oxide/graphene nanocomposites for energy storage applications.