In this project we performed a theoretical study of the electrospinning process. The electrospinning process typically consists of two phases. For the first part, we have studied Feng's model (2003) and used Phan-Thien Tanner (PTT) rheological model instead of Giesekus model which was used by Feng. A theoretical model for the jet is derived by using a thin filament approximation, and the resulting differential equations are solved numerically. For the second part of the jet, the basis of the modeling is the bead-spring approach first proposed by Reneker et al. (2000) and we added the evaporation effect to Reneker's model. The three dimensional equations describing the dynamics of the bending of electrospun jets are derived and the calculated behavior is compared with experimental observations of jets.