The N-doped carbon-coated LiFePO4 composite is prepared by the sol-gel method taking C2H4N4 as the nitrogen source. Meanwhile, the effect of nitrogen contents on the structure and property of LiFePO4@C is investigated. The obtained results show that the citric acid and C2H4N4 decompose insitu forming a N-doped carbon layer covering the surface of LiFePO4 particles during the sintering process, effectively enhance the electronic contact between the LiFePO4 particles, and improve the electrochemical performance of LiFePO4 electrode material. When the nitrogen content in LiFePO4@NC is 0.35 wt％, the corresponding electrode exhibits the best electrochemical performance. The initial discharge capacity of LiFePO4@N 0.35％C reaches 157.2 mAh/g at 0.1 C between 2.5 V and 4.2 V, and this capacity almost remains unchanged after 30 cycles.