The invention discloses a tooth filling composite material and a preparation method thereof. The preparation method comprises the following steps: mixing a nano-silicon powder, camphorquinone, hydroxycyclohexyl acetyl benzene and acrylic ester monomers, steaming out disperse medium and performing light curing and pulverizing to obtain a composite filler; mixing calcium dihydrogen monohydrate phosphate, calcium dihydrogen anhydrous phosphate, hydryoxyapetite, anhydrous calcium hydrogen phosphate, anhydrous magnesium sulfate, potassium chloride and monopotassium phosphate and grinding to obtaina mixed powder; and mixing the mixed powder, a solvent, an adhesive, fiber fill, a biological filling agent and the composite filler to obtain the tooth filling composite material. The problems that the traditional filling material has long setting time and relative insufficient compressive strength are solved.