The SnO2@polypyrrole (PPy) nanocomposites have been synthesized by a one-pot oxidative chemical polymerization method. The structure, composition, and morphology of the as-prepared SnO2@PPy nanocomposites are characterized by XRD, FTIR, TG, SEM, and TEM. Electrochemical investigations show that the obtained SnO2@PPy nanocomposites exhibit high discharge/charge capacities and favorable cycling when they are employed as anode materials for rechargeable lithium-ion batteries. For the SnO2@PPy nanocomposite with 79wt% SnO2, the electrode reaction kinetics is demonstrated to be controlled by the diffusion of Li+ ions in the nanocomposite. The calculated diffusion coefficiency of lithium ions in the SnO2@PPy nanocomposite with 79wt% SnO2 is 6.7×10−8 cm2 s−1, while the lithium-alloying activation energy at 0.5V is 47.3kJmol−1, which is obviously lower than that for the bare SnO2. The enhanced electrode performance with the SnO2@PPy nanocomposite is proposed to derive from the advantageous nanostructures that allow better structural flexibility, shorter diffusion length, and easier interaction with lithium.