A novel poly(methyl-methacrylate)/silica aerogel (PMMA/SA) dual-scale cellular foam was synthesized with internal mixing followed by the supercritical carbon dioxide foaming process. The effects of silica aerogel content on the microstructural and mechanical performance of the foams were investigated by SEM, TEM analysis, and mechanical tests. The experimental results suggest that the employment of silica aerogel granule as addictive can distinctly improve the morphological feature as well as the mechanical performance in comparison to neat PMMA foam by uniformizing cell size distribution, decreasing cell size and increasing cell density. And dual-scale cells including micrometric cells of 3-10 μm and nanometric cells of about 50nm existed in the structure of foams resulting from the retained original framework structure of silica aerogel, which has not been described in other studies with the addition of various fillers. Furthermore, the mechanical strength was signiifcantly elevated even with a small amount of silica aerogel resulting from the unique microstructure, decreased cell size and enhanced cell walls. The compressive strength was 18.12 MPa and the lfexural strength was 18.90 MPa by adding 5wt% and 2wt% silica aerogel, respectively. These results demonstrate the potential to synthesize PMMA/SA dual-scale cellular foams to be used as structural materials with the advantages of low density and high strength.