Mixing transition-metal phosphates Li3V2−x Fe x (PO4)3 (0≤x≤2) were first designed to be a type of intercalated and deintercalated cathodes to obtain high specific capacity for safe Li-ion batteries. Since the residual oxygen in the quartz tube furnace and pellet would oxidize the V3+ to V4+ in the Ar ambience during the sintering process, trace amounts of acetylene black inside and outside the pellet could play a role of deoxidizer to protect V3+ meanwhile ensure Fe3+ not reducing to Fe2+. With the concerted effort of inside and outside acetylene black, monoclinic structure Li3V2−x Fe x (PO4)3 (0≤x≤2) solid solutions had been successfully fabricated via a two-step synthesis method. X-ray diffractions with Rietveld refinement revealed that V1-sites were the preferred position when Fe3+ ions doped into Li3V2(PO4)3, which means, every V1-site was occupied with the same probability by V3+ and Fe3+ when 0<x<1, and then for V2-site when 1<x<2. X-ray photoelectron spectroscopy result showed the presence of trace amounts of acetylene black had realized the coexist of V3+ and Fe3+ in the Li3M2(PO4)3 framework. When evaluated as cathodes for Li-ion batteries, the pure Li3V2(PO4)3 electrode displayed the highest charge (137.2mAhg−1) and discharge (121.5mAhg−1) capacities in the first cycle, with the increase of Fe3+ content, all the charge and discharge capacities reduced drastically. Furthermore, the EIS results showed that the incorporation of the sluggish Fe3+ ions reduced the electronic conductivity and lithium conductivity, which in turn contributed to the poor electrochemical performance. Although our results did not show Fe3+/Fe2+ electrochemical activity contrary to our expectation, this preliminary study on Li3V2−x Fe x (PO4)3 (0≤x≤2) have provided a prerequisite for further improving the electrochemical properties by nanosizing and carbon-coating to better use these mixing transition-metal phosphate cathodes in the future.