The invention provides a composite nanometer material for lithium ion battery and a preparing method thereof. The preparing method includes the steps that firstly, silicon-containing sol and a vanadium compound solution are obtained; secondly, a carbon material is prepared; finally, a silicon dioxide / vanadium pentoxide / carbon composite material is obtained with the one step hydro-thermal method. The material obtained with the method is granular, the partical size is 40 nm to 120 nm, the pore diameter is 30 nm to 150 nm, the pore volume is 0.5 cm<3> / g to 1.5 cm<3> / g, and the specific area is 120 m<2> / g to 300 m<2> / g. The ternary composite nanometer material serves as a whole, the electronic conduction rate of an electrode material is increased, the charging performance and discharging performance at the large multiplying power of the electrode material are enhanced, the discharging capacity of the electrode material is magnified, the heat stability of the electrode material is improved, reduction of the battery capacity is reduced, the anti-overcharging performance of the battery is improved, and the cycling service life of the electrode material is prolonged; variation of the absolute volume is small in the charging and discharging process, the composite nanometer material has the high electrochemistry lithium storage capacity and small energy losses, and application prospects are quite broad.