Using solid-state method, a solid solution of LiFexMn1-xPO4 is generated as introducing iron into crystalline LiMnPO4 for electrochemical property improvement, and phenolic resin is added as the reducing agent and carbon sources. The Fe-to-Mn ratio that affects the electrochemical performance is also investigated, and the optimized ratio is determined. The synthesized samples have similar spherical morphology with particle size of 300~500nm, and are uniformly distributed. The results show that the electrochemical performance of LiFexMn1-xPO4 decreases continuously with increasing Mn content. The oxidation and reduction of Fe2 /Fe3 and Mn3 /Mn2 shift accordingly. The electrochemical performance by charge-discharge measurement shows: when x=0.5, the LiFe0.5Mn0.5PO4/C sample calcined at 600℃ for 10h has better performance, exhibits 147.3mAh/g at 0.1C, after 100 cycles, the discharge capacity of 115.2mAh/g becomes 112.7mAh/g, the capacity retention rate is 97.8%, illustrating well expressing its electrochemical performance at 2C. At high rate, like 10C, the capacity retention rate is 89.6% after 200 cycles.