A high-performance new silicon composite material for a negative electrode of a lithium ion battery and a preparation method thereof by utilizes a conductive polymer PEDOT and a water solution dispersant PSS as a coating layer of nano-Si powder and a carbon source. The Si/C composite material taking a Si-containing type lithium storage material as a main active substance is prepared by firstly polymerizing PEDOT: PSS on the surface of Si through in-situ polymerization reaction and then performing high-temperature carbonization treatment on a prepared Si/PEDOT: PSS composite under an inert atmosphere. The prepared composite material is doped with a small amount of S element. Nano-Si particles are uniformly embedded in a PEDOT: PSS polymer and a carbon matrix. A high yield is achieved by using cheap raw materials and a simple and environment-friendly process. The prepared Si/C composite material has very low initial irreversible capacity loss (2.8%) and excellent charge-discharge.