The invention discloses a dental filling composite material and a preparation method thereof. The preparation method comprises the following steps: mixing nano silicon power, isopropanol, dihexoxy acetyl benzene and an acrylate monomer, steaming, dispersing a medium, then light-curing and crushing to obtain a composite filler; mixing calcium dihydrogen monohydrate phosphate, anhydrous calcium dihydrogen phosphate, calcium phosphate dehydrate, anhydrous calcium hydrogen phosphate, strontium glass powder, potassium chloride and barium glass powder and then grinding to obtain mixed powder; mixingthe mixed powder, a solvent, an adhesive, a fiber filler, a biological filler and the composite filler to obtain the tooth filling composite material; the problems of long setting time and relatively-insufficient compressive strength of a traditional filling material are solved.