The Fe-Ge alloy nanoparticle and amorphous iron oxide shell (FeGe@Fe2O3) composite is synthesized by a facile arc-discharge method. The thickness of shell can be tuned regularly by the substitution of precursor. And then, the nanostructured core-shell FeGe@Fe2O3 is investigated as an anode material for lithium ion battery firstly. The FeGe@Fe2O3 harvests significantly enhanced reversible capacity of 1079.3 mA h g−1 at 0.1 A g−1 and 800 mA h g−1 retention after 50 cycles, and the capacity performance is superior to Fe-Ge alloy nanoparticles (NPs). It also shows satisfactory rate capability of 467 mA h g−1 at 2 A g−1 and 232 mA h g−1 at 5 A g−1, respectively, which is much better than bare Fe-Ge NPs. These good lithium storage performances are attributed to the amorphous oxide shell and the Fe-Ge alloy. To this end, this facile and tunable method provides a reasonable idea of controlling core-shell structure material precisely and this type of material can be large-scale synthesized.