Electrospinning has been recognized as an efficient technique for the forming of polymer nanofibers. In this project interest fabricated Soy Protein Isolate (SPI) nanofibers by electrospinning with different supply voltages, positive and negative charge. SPI was dissolved in 80%-95% w/w acetic acid solution and 80%-90% w/w formic acid solution. Only droplet formation of SPI were found instead of fibril formation, and the droplet morphology of SPI is depended on supply voltage, and type of solvent. SPI droplets from the negative supply voltage have smaller and more nodular than droplets from positive supply voltage. Formic acid SPI solution gives smaller size of droplet and more nodular than acetic acid SPI solution. In order to forming SPI nanofibers, zein/SPI blend were performed. The zein/SPI blend was studied at difference blending ratio. The 95/5 Zein/SPI was found to be the best blend composition for electrospun fiber. In addition, the effects of electrostatic distance and electrostatic voltage on electrospun fiber were also investigated. Increasing electrostatic distance or increasing voltage, smaller size of fiber was obtained.