The non poisonous, tasteless and non-polluting nano-SiO2 has excellent nanometer characterization and good compatibility with polymers, which are widely used to improve the material properties of biodegradable. The dispersion-steady theory of nano-SiO2, advance of synthetic bio-degradable materials (polylactic acid, polyvinyl alcohol, etc.) and natural polymer materials (starch, cellulose, chitosan, proteins and lignin) modified by nano-SiO2 are reviewed, and the prospect of biodegradable composites substituting for some traditional plastics in the aspects of lowering prices and improving properties is proposed.