In order to study the dispersion state of surface treatment of nanoSiO2in composites and its effects on the composites properties, the nanoSiO2was modified by silane coupling agent KH570.The modifying effects of nanoSiO2 were characterized though CA, FTIR and contact angle meter. The dispersion state of modified nanoSiO2 in woodfiber/PP were characterized by XRD and SEM, then the mechanical properties, snaking swell rate and waterabsorption of the composites were test and analyzed. The results show that when the mass fraction of KH570 is 5%, the average particle size of the modified nanoSiO2 is 62 nm, and KH570 can successfully graft on the surface of nanoSiO2.The surface modification of nanoSiO2 improves the mechanical properties of wood fiber/PP being the most excellent, also reduces the snaking swell rate and waterabsorption rate of the composites being the minimum. The tensile strength is 52.6 MPa,the bending strength is 30 MPa, the impact strength is 11.8 kJ/m2, increase by 75%, 20% and 47.5%, respectively, comparing to that unmodified adding nanoSiO2.