LiFePO4/C composite was synthesized by mechanical activation using sucrose as carbon source. High-energy ball milling facilitated phase formation during thermal treatment. TG–DSC and TPR experiments demonstrated sucrose was converted to CH x intermediate before completely decomposed to carbon. Ball milling time, calcination temperature and dwelling time all had significant impact on the discharge capacity and rate performance of the resulted power. The optimal process parameters are high-energy ball milling for 2–4h followed by thermal treatment at 700°C for 20h. The product showed a capacity of 174mAh/g at 0.1C rate and around 117mAh/g at 20C rate with the capacity fade less than 10% after 50 cycles. Too low calcination temperature or insufficient calcination time, however, could result in the residual of CH x in the electrode and led to a decrease of electrode performance.