Core-shell composite nanofibers with PA-6 (Nylon-6) as core and Poly (methyl methacrylate) (PMMA) as shell were fabricated by a coaxial electrospinning method, which were later made into nanofiber reinforced transparent composites through a hot press treatment. Morphological and structural characterizations for the composite nanofibers and the transparent composites were realized in terms of SEM, TEM, and FTIR techniques. The fiber reinforcement feature of the PA-6 was demonstrated by the SEM photos of a composite sample fractured in liquid nitrogen. Through TGA and DSC tests, it was observed that thermal endurance and glass-transition temperature of the nanofiber reinforced composites altered in variation with the contents of the reinforcing PA-6. Experimental results indicated that the mechanical performance of the nanofiber reinforced transparent composites was obviously improved, and its transparency decreased a little with an increase in the PA-6 content. As long as, however, a sacrifice of 10% in transparency was specified, an increment of more than 20% in the mechanical properties of the composites was achievable. POLYM. COMPOS., 30:239-247, 2009. (C) 2008 Society of Plastics Engineers