Firstly, nano-spherical iron phosphate was prepared by hydrothermal method, and then LiFePO4/C composite material was synthesized by carbothermal reduction method using it as a precursor. The effects of iron ion concentration in the reaction solution on the purity, structure, morphology, and particle size of iron phosphate during the preparation of nanoscale iron phosphate by hydrothermal method were studied, and the electrochemical performance of LiFePO4/C was tested. The results show that when the iron ion concentration is 2 %, the N and S impurity contents are only 19 and 27 ppm, respectively. The obtained iron phosphate has a trigonal crystal structure, the space group is P3121, and the particle size is small, about 50-100 nm, and the morphology is spherical. LiFePO4/C synthesized still retains the nano-spherical morphology, it brings good carbon coating effect and excellent electrochemical performance. The first charge-discharge specific capacity at 0.1 C rate reached 163.7 and 161.4 mAh/g, the charge-discharge efficiency was 98.6 %, and the capacity retention rate at 50 charge-discharge cycles at 1 C rate reached 98.52 %.