Abstract: A nano-Si/C composite as the anode material for a lithium-ion secondary battery was prepared by polymerization and condensation of petroleum heavy oil with dispersed nano-Si powders at 460℃ and carbonization at 900℃. The influences of adding nano-Si powders to heavy oil on yield, microstructures and electrochemical properties were investigated. Results showed that the addition of nano-Si powders is beneficial for increasing the yield of solid products. Nano-Si powders were uniformly embedded in the carbon matrix and the crystallinity of nano-Si powders had no change before and after polymerization. The nano-Si/C composite had a first reversible capacity of 498mAh/g and a cycle efficiency of 90%.