Thermodynamic analysis indicated that Li-3+.x.V-1-.x.Si-.x.O-4 film was difficult to be synthesized in aqueous solution, while Li-3V-1-.x.P-.x.O-4 could be prepared in aqueous solution. In certain alkaline aqueous solution, SiO-2 reacted with OH- and Li+ to produce Li-4SiO-4. At the same time, V-2O-5 reacted with OH- and Li+ to produce Li-3VO-4, and then Li-3VO-4 reacted with Li-4SiO-4 to produce Li-3+.x.V-1-.x.Si-.x.O-4. In this process, the reaction that produces SiO4--4 was the key step and .a.-OH-≥1.0 mol/L was a necessary condition. .a.-Li+>1.0 mol/l was a necessary condition for Li+ to react with SiO4--4 to produce Li-4SiO-4. In another alkaline aqueous solution, H-2PO--4 reacted with OH- and Li+ to produce Li-3PO-4. At the same time, V-2O-5 reacted with OH- and Li+ to produce Li-3VO-4, and then Li-3VO-4 reacted with Li-3PO-4 to produce Li-3V-1-.x.P-.x.O-4. In this process, .a.-OH->0.15 mol/L was a necessary condition for the production of VO3--4 and PO3--4. .a.-Li+>0.5 mol/L was a necessary condition for Li+ to react with VO3--4 and PO3--4 to produce Li-3VO-4 and Li-3PO-4.