Advanced　anode　materials　possessing　high　performance,　excellent　stability,　and　low　cost　are　quite　insufficient　for　sodium　ion　batteries　(NIBs),　and　there　is　a　call　for　huge　progress　to　meet　the　prerequisites　toward　practical　applications.　Herein,　a　silicon　diphosphide　(SiP2)/carbon　composite　anode　was　synthesized　by　a　facile　ball　milling　method　to　improve　the　NIBs　performance.　The　well-constructed　composite　comprised　of　uniformly　distributed　SiP2　nanocrystallites　within　a　conductive　carbon　framework　greatly　enhanced　the　electrode　conductivity　and　structural　compatibility　to　repeated　sodiation/desodiation　conversions　and　thus　generated　an　excellent　cyclability　of　＞80%　capacity　retention　for　500　cycles,　a　high　Coulombic　efficiency　of　99%,　and　a　promising　fast-rate　capability.　In-situ/ex-situ　X-ray　diffraction　and　in-situ　transmission　electron　microscopy　investigations　on　the　reversible　electrochemical　conversion　of　SiP2　showed　the　formation　of　Na3P　and　NaSi6　as　the　main　sodiation　products.　This　study　sheds　light　on　the　realization　of　large-scale,　high-performance　NIBs　through　superior　phosphorus-based　anode　materials.