A novel graphene-containing Li2FeSiO4 composite (Li2FeSiO4/C/G) has been synthesized successfully which shows superior performance when used as the cathode material for lithium ion batteries. The Li2FeSiO4/C precursor was synthesized via a modified sol-gel method and mixed with graphene oxide nanosheets which were then reduced by annealing to obtain electron conductive graphene. The structure characterizations by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) show that phase-pure Li2FeSiO4/C nanoparticles are mixed homogeneously with graphene nanosheets. When used as the cathode materials for rechargeable lithium ion batteries, the composite Li2FeSiO4/C/G shows superior large capacities and long-time cyclabilities. Specific discharge capacities of 310 mAh g−1, corresponding to 1.86 Li+ ions exchange per Li2FeSiO4 molecule, can be reached at the charging/discharging rate of 0.1C (1C=166mAg−1). At the high rate of 30C and 50C, the composite still shows ∼110 and ∼50 mAh g−1 discharge capacities after 1000 charging-discharging cyclings. These superior–the best up to now–performances of the composite are believed to be the cooperative result of the 3D conducting network, formed by the flexible and planar graphene nanosheets, and the nanoscale sizes of the carbon-coated Li2FeSiO4 particles.