Mildly expanded graphite (MEG) was synthesized by using perchloric acid as both intercalating agent and oxidizing agent. Its performance as anode material for lithium ion battery was investigated. SEM, XRD, TEM, nitrogen adsorption and TGA/DSC were used to characterize the sample. Charge/discharge tests show that the MEG exhibits a rate capacity as high as 397mAh/g at 0.2C and 250mAh/g at 1.6C.