Abstract: spidroin / silk composite nano-fibers were obtained by electrospinning with the mixed solution of Ornithoctonus huwenna spider silk / 1,1,1,3,3,3,-hexafluoro-2-propanol (HFIP) and silk / HFIP. The morphology, molecular conformations, crystallinity degree and mechanical property of the electrospun fibers were investigated by means of SEM, FT-IR, XRD and tensile test. The results indicated that spider silk protein attenuated the fiber diameter and enhanced the mechanical property of the electrospun silk fibers. The diameter of electrospun silk fibers were coarse, while with the addition of spider silk protein, the diameter of the silk / spidroin composite fibers decreased significantly, the number of fibers with diameters ＜300nm increased. The mechanical property of the electrospun fiber mat was improved by adding a certain amount of spider silk protein in the silk / HFIP solution. The FT-IR and XRD analysis showed that the content of spidroin have no regular affaction of conformation.