Nanostructured Li2FeSiO4/C cathode material is successfully synthesized through a simple co⿿precipitation method by using Fe3+ salt as iron source and polyethylene glycol as surfactant. Thermodynamic calculation is carried out to get phase predominance diagram as functions of oxygen partial pressure and temperature for Fe⿿O⿿C system, which provides effective guidance for synthesis parameter selection of pure phase Li2FeSiO4. The synthesized Li2FeSiO4/C nanoparticles show an average size of 150nm, which are composed of ultra⿿small Li2FeSiO4 nanocrystals in 10⿿25nm dispersing in amorphous carbon matrix. The in situ formed carbon network and the Li2FeSiO4 nanocrystals provide a fast transport of electron and lithium ion and thus ensure a quick electrode reaction, leading to an excellent electrochemical performance. The synthesized Li2FeSiO4/C exhibits a specific capacity of 190mAhg⿿1 at 0.1C, realizing reversible extraction/insertion of 1.37 Li+, taking into account of 16.1wt% carbon content in the composite. This work offers a simple, scalable, and low cost approach for the synthesis of high performance Li2FeSiO4/C cathode material for lithium ion batteries.