The invention relates to a preparation method of an aliphatic polycarbonate composite material. The aliphatic polycarbonate composite material is an aliphatic polycarbonate nano-composite material prepared by inorganic nanoparticles containing silicon, carbon dioxide and epoxy alkane under the effect of epoxyalkane, wherein the mass ratio of the epoxyalkane to the inorganic nanoparticles containing silicon is 100 to 0.05-4. The inorganic nanoparticles containing silicon are selected from one or more than two of optionally proportioned mixtures of polyhedral oligomeric silsesquioxane POSS and nano SiO2. The aliphatic polycarbonate composite material has good quality. The preparation method is high in efficiency, excellent in effect and suitable for industrial production.