Electrospinning was applied to prepare PEI fibrous membranes. The micro-structure of PEI fibrous membranes was studied by scanning electron microscope (SEM) and polarization infrared spectrum. The experimental results show that under the same solution concentration of PEI, the viscosity of spinning solution in the low boiling point organic solvent is higher than the viscosity in the N-methyl pyrrole (NMP), the volatility of the solvent and the viscosity of spinning solution have a great effect on the spinnability of PEI. When NMP was used as a solvent, air humidity greatly influenced the process of electrospinning and the morphology of PEI fiber. Under the same electrospinning condition, with raising the concentration of spinning solution, the parallelism of the oriented PEI fibers shows an increasing trend, and the average diameter of PEI fibers is also increasing,ranging from 400 nm to 3. 5 mu m. The dielectric properties of PEI fibrous membranes were tested by a precision impedance analyzer (4294A, Agilent) in the frequency range of 10(3) Hz to 10(7) Hz at the room temperature and under ambient atmosphere. The results indicate that the dielectric constants of PEI oriented fibers are very low, can get to 1.1, meanwhile their dielectric loss are basically unchanged, maintaining at a very low level. The receiving methods of fibers and hot-stretching can influence the dielectric properties of PEI fibrous membranes.