The surface of SiO
2 nano-particles was modified by γ-(trimethoxysily) propyl methacrylate (MPS) to prepare SiO
2-MPS, and polymethylmethacrylate (PMMA) was grafted to the SiO
2-MPS to prepare SiO
2-MPS-PMMA via in situ polymerization. The nano-SiO
2/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 SiO
2-PMS, SiO
2-MPS-PMMA, respectively. Nano-SiO
2 treated by MPS and PMMA were characterized and analyzed by FTIR and TG, and the structure of the nano-SiO
2/PMMA composites was analyzed by SEM. The impact strength, contact angle and transmittance of the nano-SiO
2/PMMA composites were also characterized. The results show that the chemical bonds are formed between nano-SiO
2 and MPS, MPS and PMMA in SiO
2-MPS/PMMA composites. The graft rate of MPS on the surface of nano-SiO
2is 10.01%, while that of PMMA is 22.95%. In contrast, SiO
2-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-SiO
2 and organic modified nano-SiO
2are slightly improved, and the transmittance reaches about 90%, up to 94.2%.