A novel one-pot chemical dealloying method has been developed to prepare nanocomposite of reduced graphene oxide (RGO) and silicon dendrite from cheap commercial Al–Si eutectic precursor. The RGO anchoring could act as both conductive agent and buffer layer for Si volume change in the application of lithium ion batteries (LIBs). The Si/RGO composites show an initial reversible capacity of 2280 mAh g−1, excellent capacity retention of 1942 mAh g−1 even after 100 cycles, and a high capacity of 1521 mAh g−1 even at the rate of 4000 mA g−1. Electrochemical impedance spectroscopy (EIS) measurement proved that Si/RGO composite has the lower charge transfer resistance. This work proposes an economic and facile method to prepare silicon based anode material for next generation LIBs with high energy density.