The invention provides a preparation method of a tin dioxide/nitrogen-doped expanded graphite composite material. The method comprises the following steps of (A) dispersing an expanded graphite flake,urea and a tin-containing precursor into absolute ethyl alcohol and stirring at 60-80 DEG C until the absolute ethyl alcohol completely volatilizes to obtain a precursor material; and (B) carbonizingthe precursor material under protective gas atmosphere and obtaining the tin dioxide/nitrogen-doped expanded graphite composite material. Nano-sized tin dioxide is uniformly embedded into a nitrogen-doped expanded graphite flake matrix, and nitrogen-doped expanded graphite not only has good conductivity, but also can inhibit volume expansion of tin dioxide particles in charging and discharging processes, thereby stabilizing the structure of an electrode. The nitrogen-doped expanded graphite of a flake structure can provide more lithium storage sites and is beneficial to release of the volumeeffect, and more channels are provided for penetration of an electrolyte. The invention further provides the tin dioxide/nitrogen-doped expanded graphite composite material.