In this paper, a type of small grain size vanadium pentoxide is prepared by a facile hydrothermal method. In different hydrothermal temperature conditions, X-ray diffraction and Raman spectrum test results display that the vanadium pentoxide prepared at 140 degrees C hydrothermal temperature has very high purity and stable layer structure. Scanning electron microscopy observes that this vanadium pentoxide displays a rather homogeneous granular morphology and the grain size can be controlled about 100-200 nm. As cathode active material for lithium-ion battery, the specific discharge capacities can achieve 243.21, 193.83 and 143.21 mAh g(-1)at 68, 170 and 340 mA g(-1)current densities. After 120 cycles, the capacity retention rate is 60.52%. In addition, in this paper this small grain size vanadium oxide is successfully used as matrix material for sulfur composite cathode of lithium-sulfur batteries. It can be found that as sulfur composite cathode at the sulfur loading mass ratio is 1:5, the specific discharge capacities can respectively reach 661.65, 514.71 and 483.13 mAh g(-1)at 68, 170 and 340 mA g(-1)current densities. After 150 cycles, the capacity retention rate can achieve 75.98%.