SiO2 nano particle,through surface modification by silicane coupling agent KH-570,was successfully applied to make nano SiO2/PP composite material by the melt-out blending process with twin-screw extruder.Effects of nano SiO2 on the reinforcing and toughening of PP were studied by analyzing the material impact broken fracture,the crystal structure and the diameter of SiO2 nano particle using SEM,XRD and TEM,respectively.Results showed that the impact strength and the tensile strength of nano SiO2/PP composite material were improved apparently;the impact strength of PP was fracture was increased to 67%when the nano SiO2 content was4%;while the nano SiO2 particle upon surfsce treatment will impose obvious heterogeneous nucleation function over PP crystal.