Abstract: The surface of SiO₂ nano-particles was modified by γ-(trimethoxysily) propyl methacrylate (MPS) to prepare SiO₂-MPS, and polymethylmethacrylate (PMMA) was grafted to the SiO₂-MPS to prepare SiO₂-MPS-PMMA via in situ polymerization. The nano-SiO₂/PMMA transparent composites were prepared via melt blending method with PMMA and the pre-dispersed masterbatch which were prepared via melt blending method with PMMA and SiO₂-PMS, SiO₂-MPS-PMMA, respectively. Nano-SiO₂ treated by MPS and PMMA were characterized and analyzed by FTIR and TG, and the structure of the nano-SiO₂/PMMA composites was analyzed by SEM. The impact strength, contact angle and transmittance of the nano-SiO₂/PMMA composites were also characterized. The results show that the chemical bonds are formed between nano-SiO₂ and MPS, MPS and PMMA in SiO₂-MPS/PMMA composites. The graft rate of MPS on the surface of nano-SiO₂is 10.01%, while that of PMMA is 22.95%. In contrast, SiO₂-MPS-PMMA has a better dispersion and lower aggregation in the PMMA. Compared to the pure PMMA, the impact strength and contact angle of the composites prepared by unmodified nano-SiO₂ and organic modified nano-SiO₂are slightly improved, and the transmittance reaches about 90%, up to 94.2%.