The invention discloses a silicon-based negative electrode material and a preparation method thereof. The method includes the following steps: adding sodium silicate solution to the inorganic acid solution till alkalinity, then washing and drying to obtain dry gel solid; pulverizing the dry gel solid, and evenly mixing the dry gel with an organic carbon source, then maintaining the mixture at an inert atmosphere or a reduced atmosphere at the temperature of 800-1000 DEG C for 6-8 h to obtain an amorphous silicon carbon composite powder; preparing an inorganic acid doped conductive polymer powder by oxidation of the monomer with an oxidant in an aqueous solution of inorganic acid, and then obtaining a basic conductive polymer powder by ammonia doping, then resolving the basic conductive polymer powder in N-methyl pyrrolidone to form a basic conductive polymer solution, then adding the amorphous silicon carbon composite powder, and performing ultrasound, and stirring treatment to disperse the powder evenly; adding acid solution to the solution to neutralize, subjecting the solution to filter, wash, and dry, then obtaining the conductive polymer coated silicon carbon negative electrode material. The silicon-based negative electrode material is used as the negative poles of lithium ion batteries, and has higher capacity and better cycle life.