Nano-sized SiO x /C composite with core–shell structure is prepared by a modified Stöber method. After heat-treatment, the O/Si ratio in SiO x /C composite is near 1 and the core of SiO x presents a structure composing of amorphous Si clusters and ordered SiO2 domains. SiO x /C composite anode shows high specific capacity (ca. 800mAhg−1), excellent cycling stability, good rate-capability but low initial coulombic efficiency. Li2O and Li4SiO4 may generate in the initial lithiation process, which, combining with the carbon shell, can buffer the volume change caused by the alloying of Si with Li, and thereby improving the cycling stability of electrode. The nano feature of SiO x /C particle and the electronic conductive nature of carbon coating layer ensure the good rate-capability of SiO x /C electrode.