Boron as a light-weight element can bond with up to five lithium ions (Li5B) in theory, which make it the highest theoretical capacity of 12395 mAh g(-1). But the use of boron-based materials as anode is mainly restricted by the chemical inertness of boron. Here, we designed an nanocomposite of reduced graphene oxide/amorphous cobalt-boride (rGO/Co-B) for anode with highly active boron as lithium ion storage sites. Because of the activated boron and conductive rGO, the rGO/Co-B electrode exhibits a considerable reversible capacity of 894 mAh g(-1) at 50 mA g(-1), a high rate performance of 547.4 mAh g(-1) at 2000 mA g(-1), and no obvious decay over 500 cycles. The synthesis of this novel anode with promising electrochemical performance reached the simple and effective use of boron, which may also provides new insights into boron-based anode materials for batteries.