A facile preparation of the LiFePO 4 /C composite is achieved through the microwave irradiation method in several minutes. Electrochemical measurements were conducted to examine the evolution of the impurity phase during the microwave heating. It is found that a short microwave heating usually leads to the existence of an amorphous, ferric intermediate, while microwave firing longer than 3min favors the formation of the Li 3 Fe 2 (PO 4 ) 3 impurity. A further calcination treatment on the microwave-derived sample has been proved to be an effective way to eliminate the ferric impurity and thus-obtained, phase-pure sample can release a capacity of 160mAhg −1 .