Gelatin is a kind of biopolymer obtained from animals and its fiber has been used as one of biocompatible dressings and sealants for many years. Electrospun gelatin nanofiber got more attention for its high specific surface area. Low toxicity gelatin nanofiber mats can be obtained by using water as the solvent in electrospinning process, but the fiber diameter below 150 nm is not easy to control and lots of beads were formed in the mats for low concentration solutions. In this study, sodium dodecyl sulfate (SDS) and ethanol were used to improve the electrospinnability of the gelatin solution with the concentration of 13 wt %. Experimental result revealed that SDS and ethanol reduced the surface tension of gelatin solution, meanwhile increased the conductivity and the viscosity. With the ratio between water and ethanol of 95 to 5, and SDS content varied from 0.3 wt % to 0.8 wt %, beads along the gelatin fibers vanished. Smooth and uniform gelatin fibers with fibers’ diameter around 110 nm were obtained.