NOVELTY - Preparing cadmium selenide nanobelt, comprises e.g. dissolving cadmium carbonate in nitric acid, heating and evaporating to obtain cadmium nitrate, magnetically stirring and incubating to form the spinning solution, electrostatically spinning, applying a direct current (DC) voltage to obtain polyvinylpyrrolidone (PVP)/cadmium nitrate composite nanobelt, placing in a program temperature control furnace for heat treatment, naturally cooling furnace body to obtain cadmium oxide nanobelt, placing the cadmium oxide nanobelt on carbon rod, transferring into a tubular furnace, heating and cooling .    USE - The method is useful for preparing cadmium selenide nanobelt.    ADVANTAGE - The cadmium selenide nanobelt is an important functional material. The method is simple, and thus suitable for large scale production.    DETAILED DESCRIPTION - Preparing cadmium selenide nanobelt, comprises: (a) dissolving cadmium carbonate as cadmium source in nitric acid, heating and evaporating to obtain cadmium nitrate, adding polyvinylpyrrolidone (PVP) as macromolecular template agent and N,N-dimethylformamide (DMF) as solvent; magnetically stirring at room temperature for 6 hours, and incubating for 3 hours to form the spinning solution, where the spinning solution is composed of 10 mass% cadmium nitrate, 20 mass% PVP and 70 mass% DMF solvent; (b) adding spinning solution into a liquid storage pipe, electrostatically spinning, where the nozzle diameter is 1 mm, and the spray head is vertical to the horizontal plane, applying a direct current (DC) voltage of 7 kV to obtain PVP/cadmium nitrate composite nanobelt, where solidifying distance is 14 cm, the room temperature is 18-25 degrees C and the relative humidity is 50-60%, placing the composite nanobelt in a program temperature control furnace for heat treatment, where the heating rate is 1 degrees C per minute, maintaining constant temperature at 500 degrees C for 4 hours, cooling to 200 degrees C at cooling speed of 1 degrees C/minute, then naturally cooling furnace body to the room temperature to obtain cadmium oxide nanobelt; (c) adding selenium powder as selenylation reagent into a small crucible, covering with a carbon rod, placing the cadmium oxide nanobelt on the carbon rod, placing the small crucible in a large crucible, adding selenium powder in the inner and outer sides of the crucible, placing upper crucible cover on the crucible outer side, and then transferring the crucible into a tubular furnace, introducing argon gas at room temperature for 30 minutes, discharging the air in the discharging pipe, heating at the speed of 1 degrees C per minute to 600 degrees C, and preserving heat for 3 hours, cooling at the cooling speed of 1 degrees C/minute to 100 degrees C, then naturally cooling to the room temperature to obtain cadmium selenide nanobelt, where the width is 2.1560 plus minus 0.2014 mu m, the thickness is 618 nm, and the length is more than 50 mu m.