Nanosized Sn–Co prepared by ultrasonic-assisted chemical reduction is milled with artificial graphite (AG) to form Sn–Co–AG composite. The as-prepared materials are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectrometry and Brunauer–Emmett–Telle (BET) surface area measurement. XRD patterns show that Sn–Co particles are poorly crystallized and artificial graphite has a typical hexagonal graphite structure phase. The diffraction peaks of Sn–Co particles remain the same but some of AG obviously change after milling Sn–Co with AG. BET areas of AG, Sn–Co and Sn–Co–AG are 1.569, 13.187 and 6.754m2 g−1, respectively. SEM images display the as-prepared Sn–Co particles have a size distribution ranging from 20 to 70nm in diameter. After milling Sn–Co with AG, Sn–Co particles keep similar morphology but there is a perceptible change in AG. Electrochemical tests show that Sn–Co–AG composite possesses much improved electrochemical performance than the state-of-the-art graphite. This composite has great potential as an alternative material for improving the energy density of a lithium ion secondary battery.