The invention provides lithium ion battery silicon substrate composite negative electrode materials and a preparation method of the lithium ion battery silicon substrate composite negative electrode materials, and belongs to the technical field of lithium ion batteries. The prepared lithium ion battery silicon substrate composite negative electrode materials comprise, 23-56 wt% of silicon, 12.1-75.4 wt% of magnesium oxide and 2-12 wt% of graphene. A magnesiothermic reduction method is adopted, and magnesium powder serves as a reducing agent for reducing oxide of silicon (SiOx, and x is larger than 0.5 and smaller than 2) to prepare silicon/magnesium oxide composite materials. Then, the magnesium oxide attached on a reaction product on the surface of the silicon serves as a catalyst. A carbon source is adopted to carry out catalytic chemical vapor deposition so as to generate the graphene. The silicon/magnesium/graphene composite negative electrode materials are prepared. According to a prepared silicon substrate lithium ion battery, after magnesiothermic reduction is carried out on the oxide of the silicon, the magnesium oxide is generated on the interior of the oxide of the silicon, a volume effect of the silicon is relieved, the magnesium oxide generated on the interior and the exterior of the oxide of the silicon has the function of the catalyst, the graphene is catalyzed and generated, the volume effect of the silicon can be further relieved, and electrical conductivity of the materials is remarkably strengthened.