The invention belongs to the field of energy materials and provides a preparation method of a tin-carbon cathode material for a lithium ion battery. The preparation method comprises the following steps: (1) a short-circuit electric arc is introduced between two metallic tin rods, the metallic tin rods are subjected to contact reaction with spraying mist of a dissolved organic carbon source aqueous solution after being evaporated by the electric arc to obtain reaction products; (2) grinding the reaction products; and (3) roasting the ground reaction products for 3-5h under the protection of an inert atmosphere at 1100-1500 DEG C, and crushing in a grading manner after roasting. In the method, a metallic oxide electric arc evaporation synthesis method is adopted to prepare a composite Sn/C cathode material for the lithium ion battery, the process is simple, the production efficiency is high, and compared with ball milling or other chemical synthetic methods, by using the method disclosed by the invention, the manufacture cost is low and the industrial production is easy; a tin raw material in a vaporized state and the atomized carbon source are subjected to the contact reaction during synthesis, tin and carbon in the prepared composite Sn/C cathode material are dispersed fully, and the disadvantage of dispersing unevenness when the other methods are implemented is overcome.