LiFePO4/C powders were synthesized by carbothermal reduction method using Li2CO3 (A.R), FePO4 (A.R) and glucose as raw materials. In this paper, the carbothermal reaction courses were characterized by Thermo-gravimetric (TG)/Differential Thermal Analysis (DTA), X-ray diffraction (XRD) and Fourier transform infrared (FTIR). It was found that the different synthesis temperatures and the different reducing atmosphere in systems could lead to different reactions, resulting in different final products and a direct impact on material performance. At around 350 °C LiFePO4 is directly formed without intermediate phase. In lower temperature of 400-500 °C, the sample included a certain amount of Li3PO4 and Fe2O3 impurity phases. When calcination temperature rose to 550 °C, the sample could be pure LiFePO4 phase.