In the present study, regenerated silk fibroin (RSF) formic acid solution and polyvinyl alcohol (PVA) aqueous solution were blended to form RSF/PVA solution. RSF formic acid solution was well compatible with PVA aqueous solution at certain RSF/PVA blending ratios. The blended solution could be electrospun to nanofibers at various RSF/PVA ratios, particularly, high RSF or PVA content in blended solution led to uniform fibers, while uneven fibers formed when RSF and PVA contents were equal or PVA content was slightly higher than RSF. Moreover, the diameter of the RSF/PVA fiber was relatively thin, which was about 100 nm.