Silicon is a remarkable candidate for lithium-ion battery anodes, due to the highest theoretical specific capacity, low working potential, and abundance on earth. However, the volume of Si changes approximate to 300% during the lithiation-delithiation cycling, leading to pulverization and poor electrical contact between Si and the current collector, resulting in fast fading capacity. To overcome these problems, we develop a novel free-standing anode by encapsulating Si nanoparticles into a lightweight, flexible, and conductive graphene network by utilizing a facile freeze-drying strategy. The Si nanoparticles are tightly anchored on the ultrathin and flexible graphene sheets, which can serve as mechanical support, electrical network, and buffer layer for Si. This free-standing aerogel exhibits superior electrochemical performance, and the specific capacity is 617 mAhg(-1) after 50 cycles at a current density of 0.8 Ag-1, 4 times that of a traditional Si electrode on Cu foil fabricated by a typical slurry method.