The nano-silicas(nano-SiO2) were prepared by reacting sodium silicate with dimethyl adipate as latent acid via the sol-gel process and characterized by Fourier transform infrared spectroscopy(FTIR), Brunauer–Emmett–Teller(BET) specific surface area, pore size distribution and transmission electron microscope (TEM). The FTIR result verified that the hydroxyl groups on the surface of the resulting nano-SiO2 form hydrogen bondings with adipic acid generated by hydrolysis of dimethyl adipate during reaction. The nano-SiO2 particles possessed a higher BET specific surface area of about 388-440 m2 g-1 depending upon the reaction temperature and their primary particle size calculated were below 10nm. TEM image showed that the nano-silica particle size were in the range of 80 to 100 nm. In addition, the low density polyethylene (LDPE) composites with different nano-SiO2 content ranging from 1-6% were prepared by the melt blending. The mechanical properties of the composites were determined. It was found that the tensile properties of all LDPE composites were improved, and the tensile strength of the composite with 3% SiO2 content increased from 6.88 to 8.32 MPa, while their broken elongation decreased gradually with increasing nano-silica loading. The thermal decomposition temperature of the LDPE composites increased slightly with increasing nano-SiO2 content.