The mechanical blending method was used to prepare the micro/nano inorganic particle modified PU-EP composites. The influence of the composition and the amount of the particles on the properties of the PU-EP composites were studied, and the toughness mechanism of the obtained composites was also discussed. The results show that the addition of nanoparticles can noticeably improve the interlaminar shear strength and the tensile strength of the PU-EP composites, while reducing the elastic modulus and changing its fracture behaviors. When the content of the nano-SiC particles equaled 2%, the interlaminar shear strength and tensile strength of the composites reached 4.47 MPa and 56.56 MPa, an improvement of about 88% and 74% compared with that of un-modified composites. Also, the temperature corresponding to different weight-losses of the nano-SiC particle modified composites was improved by about 4~8 ℃. The nanoparticles dispersed and strengthened the blunt of the silver strip, which played an important role in the course of the toughness mechanism of the composites.