Self-organization is a very common phenomenon in nature. Depending on the inherent characters, various structure and corresponding properties could be obtained. Over the past decades, materials scientists have aspired to exploit nature's assembly principles to create artificial materials. Block copolymers have attracted much research interest because they could self-organize into different nanostructure in the selective solvent. Similarly, when epoxy served as a selective solvent, block copolymers could also self-organize into nanostructure with various morphology. In this work, rigid-flexible amphiphilic block copolymer, PS-PCL-PDMS-PCL-PS (SLDLS), was designed. SLDLS block copolymers will self-organize into "core-shell" nanostructures in epoxy, where the rigid PS as the "shell" and the flexible PDMS as the "core". Due to the incorporation of the "core-shell" nanostructure, the tensile strength and toughness of the epoxy composites are simultaneously improved. When the concentration of the triblock copolymer is 20 wt%, tensile strength and the elongation at break attains 74.7MPa and 5.83%, respectively, which is 1.23 and 1.70 times that of the neat epoxy. Besides, thermal mechanical performance analysis shows that the storage modulus of all the composites are higher than that of the neat epoxy below 100 oC. It is believed that designing specific structure in epoxy resins through self-organization could provide new methods for the preparation of advanced functional epoxy composites.