A high pressure and temperature based solvothermal route was developed for the synthesis of Fe3O4 with carbon as a composite anode for lithium-ion batteries (LIBs). The carbon in products was a result of the in situ carbonization of organic components under high pressure (24.0MPa) and temperature (350°C). Composites with different amounts of carbon were prepared by annealing the solvothermal products at different temperatures. Taking advantage of the high theoretical capacity of Fe3O4 and favorable characteristics of carbon, a capacity of ~610mAhg−1 after 100 cycles was achieved for the composite with ~54.6% carbon. The carbon amount depended electrochemical performance was also investigated. The Fe3O4@C composite can be used as an alternative anode material and the introduced synthetic strategy may provide further insights into the preparation of inorganic oxides coupled with carbon via in situ carbonization of organic components.