3-Layers composite filters with glass fiber/polyacrylonitrile fiber/glass fiber structure were constructed by electrospinning the solutions prepared by polyacrylonitrile and dimethylformamide. The effects of electrospinning parameters such as solution concentration and spinning voltage on fiber morphology and the filtration performance were investigated. The results showed that nanofibers of different morphologies can be prepared by controlling the concentration of spinning solution, and the larger the fiber size with increasing the solution concentration. The spinning voltage had little effect on fiber morphology, but increasing spinning voltage can reduce the pore size of the electrospun fiber layer. Compared with glass fiber filter, the filtration efficiency of composite filters were improved significantly. The maximum steady-state efficiency can be increased by 21%, and the efficiency of most penetrate paticles size can be increased by 39%. However, when the pore size of composite filter was small, the process pressure drop showed a jump stage where the liquid film is formed on the surface of the nanofiber layer, leading to an increase in the stady-state pressure drop.