Li3V2−xLax(PO4)3/C cathode materials have been successfully synthesized by a sol-gel method. The monoclinic structure of Li3V2(PO4)3 appeared in La doped samples which show enlarged unit cell volumes compared with the sample without La doping. The doping of La influences magnetic property of Li3V2(PO4)3/C, e.g. the magnetic susceptibility of Li3V2−xLax(PO4)3/C decreases rapidly with the increasing of La content. La doped composites exhibit better electrochemical property than that of the undoped one and the Li3V1.975La0.025(PO4)3/C displays the highest capacity and best cycle stability. The Li3V1.975La0.025(PO4)3/C presents the first discharge capacity of 122.4mAhg−1 at 1C rate in the voltage range of 3.0–4.3V, 15.7% higher than that of Li3V2(PO4)3/C. And there is no capacity loss after 50 cycles. The rapid Li+ diffusion and high structural stability due to the doping of La3+ are mainly responsible for the good electrochemical performance of La doped Li3V2(PO4)3/C cathode materials.