Molecular self-assembly (MSA) has been established with nano-silver/triethylenetetramine (TETA) onto M40J graphite fiber surface. MSA facilitates the fiber surface functionalization and enabling the controlled interface structure of the fiber composite. The studies have shown that the MSA on M40J graphite fiber surface in the fiber/epoxy matrix interphase plays a critical role in the mechanical performance of the composite. Detailed surface analysis using surface enhanced Raman spectrum shows TETA being self-assembled by chemical bonds on the fiber surface, and additional insight into the enhancing interphase of the self-assembly M40J fiber/epoxy composite by scanning electron microscopy and nano-compression test. The formation of a nano-silver/TETA/epoxy interphase facilitates a stronger fracture zone relative to the untreated M40J fiber/epoxy weak interface, and increases composite strength by shifting the fracture surface away from the fiber surface. The interlaminar shear strength and the flexure strength of the MSA fiber composite have been increased 20.7% and 24.2% comparing with that of the untreated fiber composite, respectively.