The invention relates to a preparation method and an application of ultra-small VS4/Super P composite nano-powder. The preparation method comprises the following steps: adding sodium metavanadate, thioacetamide and Super P to deionized water to obtain a solution A; then dropwise adding ammonia water to the solution A to obtain a solution B with pH of 9.8-10.2; pouring the solution B into a reaction lining, and sealing the reaction lining for hydrothermal reaction; washing a reaction product with water and alcohol alternately to obtain the ultra-small VS4/Super P composite nano-powder. The VS4/Super P composite nano-powder is prepared from VS4 nano-spheres and super P nano-spheres through uniform and interactive distribution. The VS4 nano-spheres are uniform in shape and uniform in size andhave diameter of 50-80 nm. The VS4 nano-spheres are prepared from single crystal VS4 flexible nano-rods with diameter of 20 nm and length of 60-100 nm through winding, and the VS4 flexible nano-rodsgrow along the (110) crystal plane orientation. The VS4/Super P composite nano-powder is applied to lithium/sodium ion batteries and photo/electro-catalytic fields and shows excellent electrochemicaland catalytic properties.