The TPU was melted and blended with PET for improving the toughness of PET, SiO2 was added into the blend as an effective nucleating agent，two kinds of coupling agents were used to modify the nanoparticles for improving the compatibility between inorganic particles and different kinds of organic resins. The influence of the mass of TPU, nucleating agent SiO2 and coupling agents on the mechanical properties of blend were studied. The results showed that the roughness of blend increased and the strength decreased with the increase of TPU, 30% wt of TPU is a property mass for good mechanical properties. Nucleating agent nano-sized SiO2 which was 1%wt of blend could improve the ability of nucleation of PET so as to increase the strength of blend, but had little effect on the length at break. Amino silane coupling agent was better than silane coupling agent KH560 for improving the compatibility of blend.