NOVELTY - Preparation of tin-cobalt alloy/carbon nanofiber thin film cathode material comprises preparing uniform spinning solution by mixing polymer precursor e.g. polyacrylonitrile, cobalt precursor e.g. cobalt nitrate and tin precursor e.g. stannic chloride, and solvent which is dimethylformamide and/or dimethylacetamide; placing spinning solution within injection needle, extruding, and performing electrostatic spinning and film-forming; and pre-oxidizing obtained film, heating, carbonizing, heating, and naturally cooling to room temperature.    USE - Method for preparing tin-cobalt alloy/carbon nanofiber thin film cathode material for lithium ion battery.    ADVANTAGE - The tin-cobalt alloy particles are uniformly dispersed on surface of carbon nanotube fiber. The cobalt metal composition increases material electrical conductivity and at certain degree buffers the volume change of charging and discharging. The carbon fiber at the same time further buffers the volume change of the material, hence effectively improving the lithium ion battery cathode material specific capacity and cycle performance.    DETAILED DESCRIPTION - Preparation of tin-cobalt alloy/carbon nanofiber thin film cathode material comprises:    (A) preparing uniform spinning solution by mixing (g/ml) polymer precursor (0.07-0.15), cobalt precursor (0.10-1.00) and tin precursor (0.10-1.00 g/mL), where the cobalt precursor is cobalt acetate tetrahydrate, cobalt nitrate and/or cobalt chloride, the tin precursor is stannic chloride, stannous chloride, stannous octoate, and/or acetic acid, and the polymer precursor is polyacrylonitrile and/or polyvinyl pyrrolidone, and the solvent used for the solution is dimethylformamide and/or dimethylacetamide;    (B) placing the spinning solution within an injection needle having a diameter of 0.6-2 mm, applying voltage at 15 kV, extruding liquid at 0.2-1.0 mL/hour, where the distance between the needle head and receiving screen is 10-30 cm, and performing electrostatic spinning and film-forming; and    (C) pre-oxidizing obtained film in flowing air atmosphere, where the temperature increasing speed is 1-10 degrees C/minute, heating at 250-300 degrees C for 30-90 minutes, carbonizing in a flowing protective atmosphere of high purity nitrogen, heating at 700-1200 degrees C for 0.5-6 hours, and then naturally cooling to room temperature.