It is well known that the interface between the particle and matrix of the composite was significantly important as it could control the load transfer between the matrix and filler of composite. Despite of, in the polymer nanocomposites, the role of interface is still fragmented and less examined. In this paper, two different designs of interface modification were developed; molecular entanglement and chemical reaction using three variants surfactants such as ethanolamine, Jeffamine M2070 and Jeffamine XTJ502, with further investigation of structure-property relationship of epoxy/clay nanocomposites. The nanocomposites were prepared via solution mixing by reinforced 1.0–4.0 wt% of treated-clay. The interface properties were then characterized by XRD, FTIR, tensile test and fracture toughness. Results showed that for the epoxy/clay synthesized by reactive surfactant demonstrated higher stiffness and enhanced fracture toughness.