Abstract: In order to prepare the modified nano SiO₂, the glyceryl stearate dropping agent (B) was grafted on the surface of nano SiO₂ (nano SiO₂-g-B) by surface grafting firstly. Then, nano SiO₂-g-B/preirradiated-polyethylene (ir-LLDPE) composites were prepared by grafting nano SiO₂-g-B onto ir-LLDPE by a melt reacting mixing process. The structure and properties of the materials were investigated by FTIR, SEM, DSC and accelerated migration testing, etc. The results indicate that the B is grafted onto the surface of nano SiO₂. The melting temperature and the crystallization temperature of nano SiO₂-g-B/ir-LLDPE composites decrease. Compared with ir-LLDPE, nano SiO₂-g-B/ir-LLDPE composites have inconspicuous changes on mechanical properties. The effective wetting duration of nano SiO₂-g-B/LLDPE composites films prepared by grafting B onto the surface of nano SiO₂ is 25 days which is 6 days longer than that of common blending, and is 1.47 times longer than that of the film made by commercial dropping agents.