Uniform Fe3O4/PPy composite nanospheres (FPCNs) with Fe3O4 nanoparticles embedded in PPy nanospheres (∼200nm) were prepared by a hydrothermal process followed by an ultrasonication assisted polymerization. For the first time, FPCNs were used as anode for lithium ion batteries, demonstrating enhanced electrochemical performance with high reversible capacity (544mAhg−1 after 300 cycles), remarkable capacity retention (98% of the initial capacity after 300 cycles), as well as good rate capability (332 mAh g−1 at 2000mAg−1). The spherical PPy matrix in FPCNs possesses three functions: 1) buffering the structural variation of Fe3O4 nanoparticles during charging/discharging process; 2) preventing the aggregation of Fe3O4 nanoparticles; 3) avoiding the direct contact between Fe3O4 nanoparticles and the electrolyte. The results observed in this study may shed some light on the investigation of MOx/polymer composite electrode materials.